Has the First Interstellar Comet Been Discovered?

Artist's illustration of a comet. Credit: NASA

Astronomers from the Minor Planet Center sent out an announcement today, hoping for astronomers to do followup observations on the comet C/2017 U1 PANSTARRS. That’s because this strange comet seems to be on a trajectory that originated outside our Solar System. Not just from the Oort Cloud, but from another star.

Is this the first insterstellar comet ever found?

Orbital path of C 2017/U1 PANSTARRS
Orbital path of C 2017/U1 PANSTARRS

Comets are broken up into two broad categories. There are the short-period comets, the ones that started out in the Kuiper Belt and follow a regular, predictable orbit that brings them close to the Sun on a regular basis. Halley’s Comet is a great example, brightening in the skies every 7 decades or so.

The long-period comets started in the Oort Cloud, a vast collection of comets extending hundreds of astronomical units from the Sun – even out to a light-year away. These comets can take hundreds of thousands or even millions of years to make the long journey down to the inner Solar System, jostled out of their holding pattern by the interaction with a nearby star.

Astronomers make several observations of a comet’s path through the Solar System and then use this to calculate its orbital eccentricity. Zero eccentricity would orbiting the Sun in a circle, while an eccentricity of 1 would be a parabolic trajectory. Halley’s Comet, for example, has an eccentricity of 0.967; somewhere between a circle and a parabola.

From the initial observations, C/2017 U1 has an eccentricity of 1.2, which makes it a hyperbolic trajectory. This means it’s on a trajectory that came from outside the Solar System itself.

Obviously a bold claim like this requires good evidence, which is why the Minor Planet Center is looking for additional observations:

Further observations of this object are very much desired. Unless there are serious problems with much of the astrometry listed below, strongly hyperbolic orbits are the only viable solutions. Although it is probably not too sensible to compute meaningful original and future barycentric orbits, given the very short arc of observations, the orbit below has e ~ 1.2 for both values. If further observations confirm the unusual nature of this orbit, this object may be the first clear case of an interstellar comet.

In a tweet, astronomer Tony Dunn included a simulation he’d made showing the trajectory of C/2017 U1 compared to other comets discovered this year.

How could a comet like this have gotten to the Solar System? When other stars pass within a few light-years of the Sun, they stir up our Oort Cloud with their gravity. Presumably the Sun does the same to other stars system cometary clouds. Three-body interactions between the comet, planets and the star could kick a comet out into an escape orbit from its star system. Actually, astronomers are arguing about the possible source in the Minor Planet Mailing List group.

Again, Tony Dunn simulated its current trajectory, showing how the comet would have been flying towards us from the Constellation Lyrae, which contains the bright star Vega. Did it come from Vega? We’ll probably never know.

C/2017 U1 was first discovered on October 18, 2017 from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) located at the Haleakala Observatory in Hawaii. The purpose of this automated telescope is to scan the sky night after night, searching for moving and variable objects. It’s one of the most prolific comet hunters in the world, which is why you probably see so many comets named after it.

The comet was about 30 million kilometers (19 million miles) from Earth, and only 6 days of observations have been made. It was traveling at a velocity of 26 km/s, much faster than the escape velocity of the Solar System.

We now know that it passed its closest point to the Sun on September 9, 2017, and is well on its way back out of the Solar System.

Will this turn out to be the first interstellar comet? It’s already as dim as magnitude 21, so astronomers will need to work quickly to gather more observations before it fades from sight entirely.

Source: Minor Planet Center

Neptune-Sized Exomoon Found Orbiting a Jupiter-Sized Planet?

Artist's impression of a hypothetical Earth-like moon around a Saturn-like exoplanet. Credit: Wikipedia Commons/ Frizaven

Finding planets beyond our Solar System is already tough, laborious work. But when it comes to confirmed exoplanets, an even more challenging task is determining whether or not these worlds have their own satellites – aka. “exomoons”. Nevertheless, much like the study of exoplanets themselves, the study of exomoons presents some incredible opportunities to learn more about our Universe.

Of all possible candidates, the most recent (and arguably, most likely) one was announced back in July 2017. This moon, known as Kepler-1625 b-i, orbits a gas giant roughly 4,000 light years from Earth. But according to a new study, this exomoon may actually be a Neptune-sized gas giant itself. If true, this will constitute the first instance where a gas giant has been found orbiting another gas giant.

The study, titled “The Nature of the Giant Exomoon Candidate Kepler-1625 b-i“, recently appeared in the scientific journal Astronomy and Astrophysics. The study was conducted by René Heller, an astrophysicist from the Max Planck Institute for Solar System Research, who examined lightcurves obtained by the Kepler mission to place constraints on the exomoon’s mass and determine its true nature.

An artist’s conception of a habitable exomoon orbiting a gas giant. Credit: NASA

Within the Solar System, moons tell us much about their host planet’s formation and evolution. In the same way, the study of exomoons is likely to provide insight into extra-solar planetary systems. As Dr. Heller explained to Universe Today via email, these studies could also shed light on whether or not these systems have habitable planets:

Moons have proven to be extremely helpful to study the formation and evolution of the planets in the solar system. The Earth’s Moon, for example, was key to set the initial astrophysical conditions, such as the total mass of the Earth and the Earth’s primordial spin state, for what has become our habitable environment. As another example, the Galilean moons around Jupiter have been used to study the conditions of the primordial accretion disk around Jupiter from which the planet pulled its mass 4.5 billion years ago. This accretion disk has long gone, but the moons that formed within the disk are still there. And so we can use the moons, in particular their contemporary composition and water contents, to study planet formation in the far past.”

When it comes to the Kepler-1625 star system, previous studies were able to produce estimates of the radii of both Kepler-1625 b and its possible moon, based on three observed transits it made in front of its star. The light curves produced by these three observed transits are what led to the theory that Kepler-1625 had a Neptune-size exomoon orbiting it, and at a distance of about 20 times the planet’s radius.

But as Dr. Heller indicated in his study, radial velocity measurements of the host star (Kepler-1625) were not considered, which would have produced mass estimates for both bodies. To address this, Dr. Heller considered various mass regimes in addition to the planet and moon’s apparent sizes based on their observed signatures. Beyond that, he also attempted to place the planet and moon into the context of moon formation in the Solar System.

Artist’s impression of an exomoon orbiting a gas giant (left) and a Neptune-sized exoplanet (right). Credit: NASA/JPL-Caltech

The first step, accroding to Dr. Heller, was to conduct estimates of the possible mass of the exomoon candidate and its host planet based on the properties that were shown in the transit lightcurves observed by Kepler.

“A dynamical interpretation of the data suggests that the host planet is a roughly Jupiter-sized (“size” in terms of radius) brown dwarf with a mass of almost 18 Jupiter masses,” he said. “The uncertainties, however, are very large mostly due to the noisiness of the Kepler data and due to the low number of transits (three). In fact, the host object could be a Jupiter-like planet or even be a moderate-sized brown dwarf of up to 37 Jupiter masses. The mass of the moon candidate ranges somewhere between a super-Earth of a few Earth masses and Neptune’s mass.”

Next, Dr. Heller compared the relative mass of the exomoon candidate and Kepler-1625 b and compared this value to various planets and moons of the Solar System. This step was necessary because the moons of the Solar System show two distinct populations, based the mass of the planets compared to their moon-to-planet mass ratios. These comparisons indicate that a moon’s mass is closely related to how it formed.

For instance, moons that formed through impacts – such as Earth’s Moon, and Pluto’s moon Charon – are relatively heavy, whereas moons that formed from a planet’s accretion disk are relatively light. While Jupiter’s moon Ganymede is the most massive moon in the Solar System, it is rather diminutive and tiny compared to Jupiter itself – the largest and most massive body in the Solar System.

Artist’s impression of the view from a hypothetical moon around a exoplanet orbiting a triple star system. Credit: NASA

In the end, the results Dr. Heller obtained proved to be rather interesting. Basically, they indicated that Kepler-1625 b-i cannot be definitively placed in either of these families (heavy, impact moons vs. lighter, accretion moons). As Dr. Heller explained:

“[T]]he most reasonable scenarios suggest that the moon candidate is more of the heavy kind, which suggests it should have formed through an impact. However, this exomoon, if real, is most likely gaseous. The solar system moons are all rocky/icy bodies without a significant gas envelope (Titan has a thick atmosphere but its mass is negligible). So how would a gas giant moon have formed through an impact? I don’t know. I don’t know if anybody knows.

“Alternatively, in a third scenario, Kepler-1625 b-i could have formed through capture, but this implies a very unlikely progenitor planetary binary system, from which it was pulled into a bound orbit around Kepler-1625 b, while its former planetary companion was ejected from the system.”

What was equally interesting were the mass estimates for Keple-1625 b, which Dr. Heller averaged to be 19 Jupiter masses, but could be as high as 112 Jupiter Masses. This means that the host planet could be anything from a gas giant that is just slightly larger than Saturn to a Brown Dwarf or even a Very-Low-Mass-Star (VLMS). So rather than a gas giant moon orbiting a gas giant, we could be dealing with a gas giant moon orbiting a small star, which together orbit a larger star!

An artist’s conception of a T-type brown dwarf. Credit: Tyrogthekreeper/Wikimedia Commons.

It’s the stuff science fiction is made of! And while this study cannot provide exact mass constraints on Keplder-1625 b and its possible moon, its significance cannot be denied. Beyond providing astrophysicists with the first possible example of a gas giant moon, this study is of immense significance as far as the study of exoplanet systems is concerned. If and when Kepler-1625 b-i is confirmed, it will tell us much about the conditions under which its host formed.

In the meantime, more observations are needed to confirm or rule out the existence of this moon. Fortunately, these observations will be taking place in the very near future. When Kepler-1625 b makes it next transit – on October 29th, 2017 – the Hubble Space Telescope will be watching! Based on the light curves it observes coming from the star, scientist should be able to get a better idea of whether or not this mysterious moon is real and what it looks like.

“If the moon turns out to be a ghost in the data, then most of this study would not be applicable to the Kepler-1625 system,” said Dr. Heller. “The paper would nevertheless present an example study of how to classify future exomoons and how to put them into the context of the solar system. Alternatively, if Kepler-1625 b-i turns out to be a genuine exomoon, then my study suggests that we have found a new kind of moon that has a very different formation history than the moons we know as of today. Certainly an exquisite riddle for astrophysicists to solve.”

The study of exoplanet systems is like pealing an onion, albeit in a dark room with the lights turned off. With every successive layer scientists peel back, the more mysteries they find. And with the deployment of next-generation telescopes in the near future, we are bound to learn a great deal more!

Further Reading: Astronomy and Astrophysics

Water Worlds Don’t Stay Wet for Very Long

Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)
Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)

When hunting for potentially habitable exoplanets, one of the most important things astronomers look for is whether or not exoplanet candidates orbit within their star’s habitable zone. This is necessary for liquid water to exist on a planet’s surface, which in turn is a prerequisite for life as we know it. However, in the course of discovering new exoplanets, scientists have become aware of an extreme case known as “water worlds“.

Water worlds are essentially planets that are up to 50% water in mass, resulting in surface oceans that could be hundreds of kilometers deep. According to a new study by a team of astrophysicists from Princeton, the University of Michigan and Harvard, water worlds may not be able to hang on to their water for very long. These findings could be of immense significance when it comes to the hunt for habitable planets in our neck of the cosmos.

This most recent study, titled “The Dehydration of Water Worlds via Atmospheric Losses“, recently appeared in The Astrophysical Journal Letters. Led by Chuanfei Dong from the Department of Astrophysical Sciences at Princeton University, the team conducted computer simulations that took into account what kind of conditions water worlds would be subject to.

Artist’s impression of the planet orbiting a red dwarf star. Credit: ESO/M. Kornmesser

This study was motivated largely by the number of exoplanet discoveries have been made around low-mass, M-type (red dwarf) star systems in recent years. These planets have been found to be comparable in size to Earth – which indicated that they were likely terrestrial (i.e. rocky). In addition, many of these planets – such as Proxima b and three planets within the TRAPPIST-1 system – were found to be orbiting within the stars habitable zones.

However, subsequent studies indicated that Proxima b and other rocky planets orbiting red dwarf stars could in fact be water worlds. This was based on mass estimates obtained by astronomical surveys, and the built-in assumptions that such planets were rocky in nature and did not have massive atmospheres. At the same time, numerous studies have been produced that have cast doubt on whether or not these planets would be able to hold onto their water.

Basically, it all comes down to the type of star and the orbital parameters of the planets. While long-lived, red dwarf stars are known for being variable and unstable compared to our Sun, which results in periodic flares up that would strip a planet’s atmosphere over time. On top of that, planets orbiting within a red dwarf’s habitable zone would likely be tidally-locked, meaning one side of the planet would be constantly exposed to the star’s radiation.

Because of this, scientists are focused on determining just how well exoplanets in different types of star systems could hold onto their atmospheres. As Dr. Dong told Universe Today via email:

“It is fair to say that the presence of an atmosphere is perceived as one of the requirements for the habitability of a planet. Having said that, the concept of habitability is a complex one with myriad factors involved. Thus, an atmosphere by itself will not suffice to guarantee habitability, but it can be regarded as an important ingredient for a planet to be habitable.”

Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech
Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech

To test whether or not a water world would be able to hold onto its atmosphere, the team conducted computer simulations that took into account a variety of possible scenarios. These included the effects of stellar magnetic fields, coronal mass ejections, and atmospheric ionization and ejection for various types of stars – including G-type stars (like our Sun) and M-type stars (like Proxima Centauri and TRAPPIST-1).

With these effects accounted for, Dr. Dong and his colleagues derived a comprehensive model that simulated how long exoplanet atmospheres would last. As he explained it:

“We developed a new multi-fluid magnetohydrodynamic model. The model simulated both the ionosphere and magnetosphere as a whole. Due to the existence of the dipole magnetic field, the stellar wind cannot sweep away the atmosphere directly (like Mars due to the absence of a global dipole magnetic field), instead, the atmospheric ion loss was caused by the polar wind.

“The electrons are less massive than their parent ions, and as a result, are more easily accelerated up to and beyond the escape velocity of the planet. This charge separation between the escaping, low-mass electrons and significantly heavier, positively-charged ions sets up a polarization electric field. That electric field, in turn, acts to pull the positively charged ions along behind the escaping electrons, out of the atmosphere in the polar caps.”

Artist’s impression of the view from the most distant exoplanet discovered around the red dwarf star TRAPPIST-1. Credit: ESO/M. Kornmesser.

What they found was that their computer simulations were consistent with the current Earth-Sun system. However, in some extreme possibilities – such as exoplanets around M-type stars – the situation is very different and the escape rates could be one thousand times greater or more. The result means that even a water world, if it orbits an red dwarf star, could lose its atmosphere after about a gigayear (Gyr), one billion years.

Considering that life as we know it took around 4.5 billion years to evolve, one billion years is a relatively brief window. In fact, as Dr. Dong explained, these results indicate that planets that orbit M-type stars would be hard pressed to develop life:

“Our results indicate that the ocean planets (orbiting a Sun-like star) will retain their atmospheres much longer than the Gyr timescale as the ion escape rates are far too low, therefore, it allows a longer duration for life to originate on these planets and evolve in terms of complexity. In contrast, for exoplanets orbiting M-dwarfs, they could have their oceans depleted over the Gyr timescale due to the more intense particle and radiation environments that exoplanets experience in close-in habitable zones. If the atmosphere were to be depleted over the timescale less than Gyr, this could prove to be problematic for the origin of life (abiogenesis) on the planet.”

Once again, these results cast doubt on the potential habitability of red dwarf star systems. In the past, researchers have indicated that the longevity of red dwarf stars, which can remain in their main sequence for up to 10 trillion years or longer, make them the best candidate for finding habitable exoplanets. However, the stability of these stars and the way in which they are likely to strip planets of their atmospheres seems to indicate otherwise.

An artist’s depiction of planets transiting a red dwarf star in the TRAPPIST-1 System. Credit: NASA/ESA/STScl

Studies such as this one are therefore highly significant in that they help to address just how long a potentially habitable planet around a red dwarf star could remain potentially habitable. As Dr. Dong indicated:

“Given the importance of atmospheric loss on planetary habitability, there has been a great deal of interest in using telescopes such as the upcoming James Webb Space Telescope (JWST) to determine whether these planets have atmospheres and, if so, what their composition are like. It is expected that the JWST should be capable of characterizing these atmospheres (if present), but quantifying the escape rates accurately requires a much higher degree of precision and may not be feasible in the near-future.”

The study is also significant as far as our understanding of the Solar System and its evolution is concerned. At one time, scientists have ventured that both Earth and Venus may have been water worlds. How they made the transition from being very watery to what they are today – in the case of Venus, dry and hellish; and in the case of Earth, having multiple continents – is an all-important question.

In the future, more detailed surveys are anticipated that could help shed light on these competing theories. When the James Webb Space Telescope (JWST) is deployed in Spring of 2018, it will use its powerful infrared capabilities to study planets around nearby red dwarfs, Proxima b being one of them. What we learn about this and other distant exoplanets will go a long way towards informing our understanding of how our own Solar System evolved as well.

Further Reading: CfA, The Astrophysical Journal Letters

What is an Electric Sail? Another Exotic Way to Explore the Solar System

What Is An Electric Sail?
What Is An Electric Sail?

We’re all familiar with the idea of solar sails to explore the Solar System, using the light pressure from the Sun. But there’s another propulsion system that could harness the power of the Sun, electric sails, and it’s a pretty exciting idea.

A few weeks ago, I tackled a question someone had about my favorite exotic propulsion systems, and I rattled off a few ideas that I find exciting: solar sails, nuclear rockets, ion engines, etc. But there’s another propulsion system that keeps coming up, and I totally forgot to mention, but it’s one of the best ideas I’ve heard in awhile: electric sails.

Artist concept of a solar sail demonstration mission that will use lasers for navigation. Credit: NASA.
Artist concept of a solar sail demonstration mission that will use lasers for navigation. Credit: NASA.

As you probably know, a solar sail works by harnessing the photons of light streaming from the Sun. Although photons are massless, they do have momentum, and can transfer it when they bounce off a reflective surface.

In addition to light, the Sun is also blowing off a steady stream of charged particles – the solar wind. A team of engineers from Finland, led by Dr. Pekka Janhunen, has proposed building an electric sail that will use these particles to carry spacecraft out into the Solar System.

To understand how this works, I’ll need to jam a few concepts into your brain.

First, the Sun. That deadly ball of radiation in the sky. As you probably know, there’s a steady stream of charged particles, mainly electrons and protons, zipping away from the Sun in all directions.

Visualization of the solar wind encountering Earth's magnetic "defenses" known as the magnetosphere. Clouds of southward-pointing plasma are able to peel back layers of the Sun-facing bubble and stack them into layers on the planet's nightside (center, right). The layers can be squeezed tightly enough to reconnect and deliver solar electrons (yellow sparkles) directly into the upper atmosphere to create the aurora. Credit: JPL
Visualization of the solar wind encountering Earth’s magnetic “defenses” known as the magnetosphere. Clouds of southward-pointing plasma are able to peel back layers of the Sun-facing bubble and stack them into layers on the planet’s nightside (center, right). The layers can be squeezed tightly enough to reconnect and deliver solar electrons (yellow sparkles) directly into the upper atmosphere to create the aurora. Credit: JPL

Astronomers aren’t entirely sure how, but some mechanism in the Sun’s corona, its upper atmosphere, accelerates these particles on an escape velocity. Their speed varies from 250 to 750 km/s.

The solar wind travels away from the Sun, and out into space. We see its effects on comets, giving them their characteristic tails, and it forms a bubble around the Solar System known as the heliosphere. This is where the solar wind from the Sun meets the collective solar winds from the other stars in the Milky Way.

In fact, NASA’s Voyager spacecraft recently passed through this region, finally making their way to interstellar space.

The solar wind does cause a direct pressure, like an actual wind, but it’s incredibly weak, a fraction of the light pressure a solar sail experiences.

This artist's concept shows the Voyager 1 spacecraft entering the space between stars. Interstellar space is dominated by plasma, ionized gas (illustrated here as brownish haze), that was thrown off by giant stars millions of years ago.Credit: NASA.
This artist’s concept shows the Voyager 1 spacecraft entering the space between stars. Interstellar space is dominated by plasma, ionized gas (illustrated here as brownish haze), that was thrown off by giant stars millions of years ago.Credit: NASA.

But the solar wind contains a stream of positively charged protons and electrons, and this is the key.

An electric sail works by reeling out an incredibly thin wire, just 25 microns thick, but 20 kilometers long. The spacecraft is equipped with solar panels and an electron gun which takes just a few hundred watts to run.

By shooting electrons off into space, the spacecraft maintains a highly positive charged state. Since the protons from the Sun are also positively charged, when they encounter the positively charged tether, they “see” it a huge obstacle 100 meters across, and crash into it.

By imparting their momentum into the tether and spacecraft, the ions accelerate it away from the Sun.

The amount of acceleration is very weak, but it’s constant pressure from the Sun and can add up over a long period of time. For example, if a 1000 kg spacecraft had 100 of these wires extending out in all directions, it could receive an acceleration of 1 mm per second per second.

In the first second it travels 1 mm, and then 2 mm in the next second, etc. Over the course of a year, this spacecraft could be going 30 km/s. Just for comparison, the fastest spacecraft out there, NASA’s Voyager 1, is merely going about 17 km/s. So, much faster, definitely on an escape velocity from the Solar System.

One of the downsides of the method, actually, is that it won’t work within the Earth’s magnetosphere. So an electric sail-powered spacecraft would need to be carried by a traditional rocket away from the Earth before it could unfurl its sail and head out into deep space.

I’m sure you’re wondering if this is a one-way trip to get away from the Sun, but it’s actually not. Just like with solar sails, a electric sail can be pivoted. Depending on which side of the sail the solar wind hits, it either raises or lowers the spacecraft’s orbit from the Sun.

Strike the sail on one side and you raise its orbit to travel to the outer Solar System. But you could also strike the other side and lower its orbit, allowing it to journey down into the inner Solar System. It’s an incredibly versatile propulsion system, and the Sun does all the work.

Although this sounds like science fiction, there are actually some tests in the works. An Estonian prototype satellite was launched back in 2013, but its motor failed to reel out the tether. The Finnish Aalto-1 satellite was launched in June 2017, and one of its experiments is to test out an electric sail.

We should find out if the technique is viable later this year.

It’s not just the Finns who are considering this propulsion system. In 2015, NASA announced that they had awarded a Phase II Innovative Advanced Concepts grant to Dr. Pekka Janhunen and his team to explore how this technology could be used to reach the outer Solar System in less time than other methods.

The Heliopause Electrostatic Rapid Transit System, or HERTS spacecraft would extend 20 of these electric tethers outward from the center, forming a huge circular electric sail to catch the solar wind. By slowly rotating the spacecraft, the centrifugal forces will stretch the tethers out into this circular shape.

Artist's illustration of NASA's Heliopause Electrostatic Rapid Transit System.  Credit: NASA
Artist’s illustration of NASA’s Heliopause Electrostatic Rapid Transit System. Credit: NASA

With its positive charge, each tether acts like a huge barrier to the solar wind, giving the spacecraft an effective surface area of 600 square kilometers once it launches from the Earth. As it gets farther, from Earth, though, its effective area increases to the equivalent of 1,200 square km by the time it reaches Jupiter.

When a solar sail starts to lose power, an electric sail just keeps accelerating. In fact, it would keep accelerating out past the orbit of Uranus.

If the technology works out, the HERTS mission could reach the heliopause in just 10 years. It took Voyager 1 35 years to reach this distance, 121 astronomical units from the Sun.

But what about steering? By changing the voltage on each wire as the spacecraft rotates, you could have the whole sail interact differently on one side or the other to the solar wind. You could steer the whole spacecraft like the sails on a boat.

In September 2017, a team of researchers with the Finnish Meteorological Institute announced a pretty radical idea for how they might be able to use electric sails to comprehensively explore the asteroid belt.

Instead of a single spacecraft, they proposed building a fleet of 50 separate 5-kg satellites. Each one would reel out its own 20 km-long tether and catch the Sun’s solar wind. Over the course of a 3-year mission, the spacecraft would travel out to the asteroid belt, and visit several different space rocks. The full fleet would probably be able to explore 300 separate objects.

This image depicts the two areas where most of the asteroids in the Solar System are found: the asteroid belt between Mars and Jupiter, and the trojans, two groups of asteroids moving ahead of and following Jupiter in its orbit around the Sun.

Each spacecraft would be equipped with a small telescope with only a 40 mm aperture. That’s about the size of a spotting scope, or half a pair of binoculars, but it would be enough to resolve features on the surface of an asteroid as small as 100 meters across. They’d also have an infrared spectrometer to be able to determine what minerals each asteroid is made of.

That’s a great way to find that $10 trillion asteroid made of solid platinum.

Because the spacecraft would be too small to communicate all the way back to Earth, they’d need to store the data on board, and then transmit everything once they came past our planet 3 years later.

The planetary scientists I’ve talked to love the idea of being able to survey this many different objects at the same time, and the electric sail idea is one of the most efficient methods to do it.

According to the researchers, they could do the mission for about $70 million, bringing the cost to analyze each asteroid down to about $240,000. That would be cheap compared to any other method proposed of studying asteroids.

Space exploration uses traditional chemical rockets because they’re known and reliable. Sure they have their shortcomings, but they’ve taken us across the Solar System, to billions of kilometers away from Earth.

But there are other forms of propulsion in the works, like the electric sail. And over the coming decades, we’re going to see more and more of these ideas put to the test. A fuel free propulsion system that can carry a spacecraft into the outer reaches of the Solar System? Yes please.

I’ll keep you posted when more electric sails are tested.

You Can Now Use Google Maps to Explore the Solar System

Google Maps now lets users explore the Solar System. Credit: NASA/Google

Chances are, at one time or another, we’ve all used Google Maps to find the shortest route from point A to point B. But if you are like some people, you’ve used this mapping tool to have a look at geographical features or places you hope to visit someday. In an age where digital technology is allowing for telecommuting and even telepresence, it’s nice to take virtual tours of the places we may never get to see in person.

But now, Google Maps is using its technology to enable the virtual exploration of something far grander: the Solar System! Thanks to images provided by the Cassini orbiter of the planets and moons it studied during its 20 year mission, Google is now allowing users to explore places like Venus, Mercury, Mars, Europa, Ganymede, Titan, and other far-off destinations that are impossible for us to visit right now.

Similar to how Google Earth uses satellite imagery to create 3D representations of our planet, this new Google Maps tool relies on the more than 500,000 images taken by Cassini as it made its way across the Solar System. This probe recently concluded its 20 year mission, 13 of which were spent orbiting Saturn and studying its system of moons, by crashing into the atmosphere of Saturn.

Artist rendition of the Cassini spacecraft over Saturn. Credit: NASA/JPL-Caltech/SSI/Kevin M. Gill.

After launching from Earth on October 15th, 1997, Cassini conducted a flyby of Venus in order to pick up a gravity-assist. It then flew by Earth, obtaining a second gravity-assist, while making its way towards the Asteroid Belt. Before reaching the Saturn System, where it would begin studying the gas giant and its moons, Cassini also conducted a flyby of Jupiter – snapping pictures of its moons, rings, and Great Red Spot.

When it reached Saturn in July of 2004, Cassini went to work studying the planet and its larger moons – particularly Titan and Enceladus. During the next 13 years and 76 days, the probe would provide breathtaking images and sensor data on Saturn’s rings, atmosphere and polar storms and reveal things about Titan’s surface that were never before seen (such as its methane lakes, hydrological cycle, and surface features).

It’s flybys of Enceladus also revealed some startling things about this icy moon. Aside from detecting a tenuous atmosphere of ionized water vapor and Enceladus’ mysterious “Tiger Stripes“, the probe also detected jets of water and organic molecules erupting from the moon’s southern polar region. These jets, it was later determined, were indicative of a warm water ocean deep in the moon’s interior, and possibly even life!

Interestingly enough, the original Cassini mission was only planned to last for four years once it reached Saturn – from June 2004 to May 2008. But by the end of this run, the mission was extended with the Cassini Equinox Mission, which was intended to run until September of 2010. It was extended a second time with the Cassini Solstice Mission, which lasted until September 15th, 2017, when the probe was crashed into Saturn’s atmosphere.

Artist’s impression of the Cassini orbiter entering Saturn’s atmosphere. Credit: NASA/JPL

Thanks to all the images taken by this long-lived mission, Google Maps is now able to offer exploratory tours of 16 celestial bodies in the Solar System – 12 of which are new to the site. These include Earth, the Moon, Mercury, Venus, Mars, Pluto, Ceres, Io, Europa, Ganymede, Mimas, Enceladus, Dione, Rhea, Titan, Iapetus and (available as of July 2017) the International Space Station.

This latest development also builds on several extensions Google has released over the years. These include Google Moon, which was released on July 20th, 2005, to coincide with the 36th anniversary of the Apollo 11 Moon Landing. Then there was Google Sky (introduced in 2007), which used photographs taken by the Hubble Space Telescope to create a virtual map of the visible universe.

Then there was Google Mars, the result of a collaborative effort between Google and NASA scientists at the Mars Space Flight Facility released in 2011, one year before the Curiosity rover landed on the Red Planet. This tool relied on data collected by the Mars Global Surveyor and the Mars Odyssey missions to create high-resolution 3D terrain maps that included elevations.

In an age of high-speed internet and telecommunications, using the internet to virtually explore the many planets and bodies of the Solar System just makes sense. Especially when you consider that even the most ambitious plans to conduct tourism to Mars or the Moon (looking at you, Elon Musk and Richard Branson!) are not likely to bear fruit for many years, and cost an arm and a leg to boot!

In the future, similar technology could lead to all kinds of virtual exploration. This concept, which is often referred to as “telexploration”, would involve robotic missions traveling to other planets and even star systems. The information they gather would then be sent back to Earth to create virtual experiences, which would allow scientists and space-exploration enthusiasts to feel like they were seeing it firsthand.

In truth, this mapping tool is just the latest gift to be bestowed by the late Cassini mission. NASA scientists expect to be sifting through the volumes of data collected by the orbiter for years to come. Thanks to improvements made in software applications and the realms of virtual and augmented reality, this data (and that of present and future missions) is likely to be put to good use, enabling breathtaking and educational tours of our Universe!

Further Reading: Make Use Of

Covert NRO Satellite Fades into Capes Cloudy Night Skies Shrouded in Liftoff Secrecy: Gallery – As ULA Atlas Wins Landsat Launch

Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

CAPE CANAVERAL AIR FORCE STATION, FL — As one Atlas rocket carrying a covert spy satellite for the U.S. National Reconnaissance Office (NRO) to monitor Earth for national security purposes faded into cloudy nighttime skies over the Cape in the dead of night shrouded in liftoff secrecy, rocket builder United Launch Alliance (ULA) won another significant Atlas launch contract for NASA’s Landsat 9 satellite to monitor the health of Earth’s environment.

Capping two launches from two different rocket companies in four days by ULA and SpaceX followed by the arrival back in port of SpaceX’s ocean landed recovered booster, last week provided all the proof that’s needed to demonstrate that the revitalization of Florida’s Spaceport is well underway and America’s rocket makers are capturing lucrative launch contracts ensuring an upswing nationwide in rocket and spacecraft manufacturing – for critical military surveillance, government, civilian and science needs.

Check out the exciting gallery of Atlas launch imagery and videos including the thrilling droneship return of SpaceX’s 156 foot tall first stage booster back into Port Canaveral less than 4 hours after ULA delivered the classified NROL-52 surveillance satellite to a secret orbit – from this author and several space media colleagues. And check back here as the gallery grows!

A ULA Atlas V launch carrying the covert NROL-52 mission in support of U.S. national security blasted off overnight Sunday, Oct. 15 at 3:28 a.m. EDT (0728 GMT) from seaside Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida.

“Congratulations to the team who helped make #NROL52 a success! United Launch Alliance, 45th Space Wing at Patrick Air Force Base, Fla., Air Force Space Command, and the Space and Missile Systems Center,” the NRO announced post launch on social media.

It was a case of ‘Going, Going, Gone’ as seemingly endless stormy weather plagued the space coast and the Atlas soon disappeared behind clouds from many but not all vantage points, as the two stage rocket was finally cleared to launch on its fifth try. Postponed three times by poor weather and once due to a technical glitch to fix a faulty second stage transmitter.

Reflecting in a pond a United Launch Alliance (ULA) Atlas V rocket blasts off with the covert NROL-52 spy satellite for the National Reconnaissance Office at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

The launches were postponed by the downstream impact of Hurricane Irma which forced the base closings of the Kennedy Space Center and Cape Canaveral Air Force Station and significantly impacted the Florida Space Coast region by causing over $100 million in damage to buildings, homes, businesses, hotels, restaurants, infrastructure and more due to flooding and hurricane force winds.

“We’ve had an incredible month,” said Brig. Gen. Wayne R. Monteith, Commander, 45th Space Wing.

“Not only did we restore our base to full mission capable status just a few hours after Hurricane Irma impacted our coast, but we’ve successfully launched two rockets in less than four days just weeks later.”

Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

“The 45th Space Wing supported ULA’s Atlas V launch of the NROL-52 mission for the National Reconnaissance Office early morning on Oct. 15!”

“The men and women of the 45th Space Wing continue to make the impossible possible.”

Reflecting in a pond a United Launch Alliance (ULA) Atlas V rocket blasts off with the covert NROL-52 spy satellite for the National Reconnaissance Office at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

More than a quarter of all the world’s rocket launches take place from Florida’s burgeoning spaceports.

Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

“Our team’s resiliency and tireless efforts in launching over 25% of all world-wide launches this year proves why we are the ‘World’s Premier Gateway to Space,’” Montieth gushed in pride.

Meanwhile, NASA selected ULA to provide launch services for the Landsat 9 mission with another Atlas V rocket as soon as late 2020.

“The mission is currently targeted for a contract launch date of June 2021, while protecting for the ability to launch as early as December 2020, on an Atlas V 401 rocket from Space Launch Complex 3E at Vandenberg Air Force Base in California,” said NASA.

The Landsat 9 launch contract is worth $153.8 million.

Landsat 9 is a joint mission between NASA and the U.S. Geological Survey (USGS).

“Landsat 9 will continue the Landsat program’s critical role in monitoring, understanding, and managing the land resources needed to sustain human life.”

“We are honored that NASA has entrusted ULA with launching this critical land imaging satellite,” said Tory Bruno, ULA’s president and chief executive, in a statement.

“ULA’s world-leading performance and reliability, paired with the tremendous heritage of 74 consecutive successful Atlas V launches, provides the optimal value for our customer. We look forward to working together again with our mission partners at NASA’s Launch Services Program, Goddard Space Flight Center and the U.S. Geological Survey in the integration and launch of this significant mission, contributing to the international strategy for examining the health and state of the Earth.”

ULA Atlas V rocket streaks to orbit in this long duration exposure carrying covert NROL-52 payload for the NRO after lift off from Space Launch Complex-41 on Oct. 15, 2017 at 3:28 a.m. EDT at Cape Canaveral Air Force Station in Florida. Credit: Jeff Seibert

NROL-52 is the fourth of five launches slated for the NRO in 2017 by both ULA and SpaceX.

“Never before has innovation been more important for keeping us ahead of the game. As the eagle soars, so will the advanced capabilities this payload provides to our national security,” said Colonel Matthew Skeen, USAF, Director, NRO Office of Space Launch, in a statement. “Kudos to the entire team for a job well done.”

Check out this exciting video compilation from remote cameras circling the Atlas pad 41.

Video Caption: Launch of the NROL-52 satellite on an Atlas 5 booster from Pad 41. A United Launch Alliance Atlas 5 421 rocket launches the NROL-52 payload on Oct. 15, 2017 at 328 a.m. EDT on the 5th launch attempt. Previous launch attempts were halted by weather issues 3 times, and a faulty telemetry radio that needed to be replaced after the rocket was rolled back to the Pad 41 Vertical Integration Facility. Credit Jeff Seibert

The venerable two stage Atlas V stands 194 feet tall and sports a 100% success record. The first stage generates approx. 1.6 million pounds of liftoff thrust.

This Atlas Evolved Expendable Launch Vehicle (EELV) mission launched in the 421 configuration vehicle, which includes a 4-meter payload fairing (PLF) encapsulating the payload and two strap on solid rocket first stage boosters.

The Atlas first stage booster for this mission was powered by the Russian-built RD AMROSS RD-180 engine, and the Centaur upper stage was powered by the Aerojet Rocketdyne RL10C-1 engine.

The dual chamber, dual-nozzle RD-180 is fueled by a mixture of RP-1 kerosene and LOX (liquid oxygen).

The ULA Atlas V first stage powers NROL-52 spy satellite to orbit for the NRO firing the dual chamber, dual-nozzle RD-180 engines after blastoff at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

The next NRO launch is scheduled on a ULA Delta IV in December from Vandenberg Air Force Base, California.

Reflecting in a pond a United Launch Alliance (ULA) Atlas V rocket blasts off with the covert NROL-52 spy satellite for the National Reconnaissance Office at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

Watch for Ken’s continuing onsite NROL-52, SpaceX SES-11 and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Liftoff of ULA Atlas V rocket carrying classified NROL-52 payload for the NRO on Oct. 15, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Julian Leek
United Launch Alliance (ULA) Atlas V rocket streaks to orbit in this long duration exposure carrying covert NROL-52 payload for the National Reconnaissance Office after lift off from Space Launch Complex-41 on Oct. 15, 2017 at 3:28 a.m. EDT at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
Reflecting in a pond a ULA Atlas V rocket stands poised for launch with the NROL-52 surveillance satellite for the National Reconnaissance Office prior to blastoff on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
Reflown SpaceX Falcon 9 first stage booster arrives at sunrise atop OCISLY droneship being towed into the mouth of Port Canaveral, FL on Oct. 15, 2017 after successfully launch SES-11 UHDTV comsat to orbit on Oct. 11, 2017. Credit: Ken Kremer/Kenkremer.com
ULA Atlas V rocket blasts off carrying covert NROL-52 payload for the NRO from Space Launch Complex-41 on Oct. 15, 2017 at 3:28 a.m. EDT at Cape Canaveral Air Force Station in Florida. Credit: Jeff Seibert

Good News Everyone! There are Fewer Deadly Undiscovered Asteroids than we Thought

An artist's impression of a Nearth-Earth Asteroid (NEA) breaking up. Credit: NASA/JPL-Caltech

Beyond Earth’s orbit, there are innumerable comets and asteroids that are collectively known as Near-Earth Objects. On occasion, some of these objects will cross Earth’s orbit; and every so often, one will pass too close to Earth and impact on its surface. While most of these objects have been too small to cause serious damage, some have been large enough to trigger Extinction Level Events (ELEs).

For this reason, NASA and other space agencies have spent decades cataloging and monitoring the larger NEAs in order to determine if they might collide with Earth at some point in the future. The only question has been, how many remain to be found? According to a recent analysis performed by Alan W. Harris of MoreData! – a California-based research company – only a handful of NEAs haven’t been catalogued yet.

These findings were the subject of a presentation made this week at the 49th annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Provo, Utah. As Harris indicated during the presentation, titled “The Population of Near-Earth Asteroids Revisited”, previous estimates of the remaining NEAs have been plagued by a consequential round-off error that have skewed the results.

Artist’s concept of the Wide-field Infrared Survey Explorer as its orbit around Earth. Credit: NASA/JPL

The source of this error has to do with how organizations that monitor NEOs determine “size-frequency distribution”. Basically, estimates are given in terms of number versus brightness, since most discovery surveys were conducted in the visible spectrum. This is not a reliable way of determining size though, since asteroids don’t all have the same albedo (aka. reflectivity).

As such, NEA brightness is expressed in units of absolute magnitude (H), where lower numbers indicate brighter objects. The IAU Minor Planet Center – which is responsible for maintaining information on asteroid and other small-body measurements – rounds off the reported values of H to the nearest 0.1 magnitude. As Harris explained during the course of his presentation:

“So, for example, a bin from H of 17.5 to 18.0 is really from 17.55 to 18.05, or 17.45 to 17.95, depending on which side of the bin you take “less than or equal to” rather than ‘less than’.”

While this has not caused much in the way of problems in the past, it has become significant as far as assessments of how many larger objects remain to be found are concerned. Harris first became aware of the potential for problems this past year after Dr. Pasqual Tricario – a Senior Scientist at the Planetary Science Institute – conducted a study that produced estimates different from those obtained by Harris and Italian astronomer Germano D’Abramo two years before.

This graphic shows asteroids and comets observed by NASA’s Near-Earth Object Wide-field Survey Explorer (NEOWISE) mission. Credit: NASA/JPL-Caltech/UCLA/JHU

The 2015 study conducted by Harris and D’Abramo – which appeared in Icarus under the title “The population of near-Earth asteroids” – yielded an estimate of 990 NEAs that were larger than 1 km in diameter. However, Tricario’s study (“The near-Earth asteroid population from two decades of observations“, also published in Icarus), which was based on the opposite “less than or equal to” assumption, produced estimates that were 10% lower.

As Harris explained, this prompted D’Adramo and him to considered a different approach. “We corrected the problem for the current analysis by choosing bin boundaries at .05 magnitudes, e.g. 17.25 to 17.75, so the 0.1 round-off thresholds naturally put objects in the right bin,” he said. “When Tricarico and I each made these corrections, our population estimates fell into almost perfect agreement.”

After applying the correction, Harris and D’Abramo’s overall estimate of undiscovered NEAs dropped from 990 to 921 ± 20. Beyond allowing for consistency between different studies, these corrected estimates also reduced the total number of undiscovered objects that remain undiscovered. According to the latest tallies from NASA’s Jet Propulsion Laboratory, 884 NEAs that are about 1 km in diameter have been discovered so far.

Based on the previous population estimate of 990 objects, this implied that the current surveys are 89% complete and 106 were yet to be found. When the corrections were applied to these numbers, JPL’s surveys now appears to be 96% complete, and only 37 objects remain to be found (almost three times less). Naturally, these new estimates depends on their own sets of assumptions, and different results can be obtained based on different criteria.

NASA is getting much better at discovering and detecting NEOs. Credit: NASA/NEO Program.

Still, a reduced estimate of undiscovered asteroids is definitely encouraging news. Especially when one considers how hazardous large asteroids are to the safety and well-being of life here on Earth. As of October 3rd, 2017, NASA’s Center for Near-Earth Object Studies (CNEOS) announced that there are a total of 157 potentially hazardous asteroids out there. Knowing that only a few more need to be found is bound to help some of us sleep at night!

Future studies are also expected to benefit from the deployment of next-generation missions. Thanks to the efforts of NASA’s Near-Earth-Object WISE (NEOWISE) mission, which looks for NEOs in the infrared band (rather than visible light), that number of known NEOs has increased substantially. With the deployment of the James Webb Space Telescope, those numbers are expected to reach even higher.

Between improvements in technology and methodology, a day may yet come when all Near-Earth Objects – be they big or small, potentially hazardous or harmless – are accounted for. Combined with asteroid defenses, like directed-energy beams or robots spacecraft capable of attaching themselves to asteroids and redirecting them, Extinction Level Events might very well become a thing of the past.

Further Reading: The Spaceguard Center

Looking for Signs of Life on Distant Planets Just Got Easier

This illustration shows a star's light illuminating the atmosphere of a planet. Credits: NASA Goddard Space Flight Center

When it comes to searching for worlds that could support extra-terrestrial life, scientists currently rely on the “low-hanging fruit” approach. Since we only know of one set of conditions under which life can thrive – i.e. what we have here on Earth – it makes sense to look for worlds that have these same conditions. These include being located within a star’s habitable zone, having a stable atmosphere, and being able to maintain liquid water on the surface.

Until now, scientists have relied on methods that make it very difficult to detect water vapor in the atmosphere’s of terrestrial planets. But thanks to a new study led by Yuka Fujii of NASA’s Goddard Institute for Space Studies (GISS), that may be about to change. Using a new three-dimensional model that takes into account global circulation patterns, this study also indicates that habitable exoplanets may be more common than we thought.

The study, titled “NIR-driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets“, recently appeared in The Astrophysical Journal. In addition to Dr. Fujii, who is also a member of the Earth-Life Science Institute at the Tokyo Institute of Technology, the research team included Anthony D. Del Genio (GISS) and David S. Amundsen (GISS and Columbia University).

Artist’s concept of the hot Jupiter WASP-121b, which presents the best evidence yet of a stratosphere on an exoplanet – generated using Engine House VFX. Credit: Bristol Science Centre/University of Exeter

To put it simply, liquid water is essential to life as we know it. If a planet does not have a warm enough atmosphere to maintain liquid water on its surface for a sufficient amount of time (on the order of billions of years), then it is unlikely that life will be able to emerge and evolve. If a planet is too distant from its star, its surface water will freeze; if it is too close, its surface water will evaporate and be lost to space.

While water has been detected in the atmospheres of exoplanets before, in all cases, the planets were massive gas giants that orbited very closely to their stars. (aka. “Hot Jupiters”). As Fujii and her colleagues state in their study:

“Although H2O signatures have been detected in the atmospheres of hot Jupiters, detecting molecular signatures, including H2O, on temperate terrestrial planets is exceedingly challenging, because of the small planetary radius and the small scale height (due to the lower temperature and presumably larger mean molecular weight).”

When it comes to terrestrial (i.e. rocky) exoplanets, previous studies were forced to rely on one-dimensional models to calculate the presence of water. This consisted of measuring hydrogen loss, where water vapor in the stratosphere is broken down into hydrogen and oxygen from exposure to ultraviolet radiation. By measuring the rate at which hydrogen is lost to space, scientists would estimate the amount of liquid water still present on the surface.

Artist’s impression of the “Venus-like” exoplanet GJ 1132b. Credit: cfa.harvard.edu

However, as Dr. Fujii and her colleagues explain, such models rely on several assumptions that cannot be addressed, which include the global transport of heat and water vapor vapor, as well as the effects of clouds. Basically, previous models predicted that for water vapor to reach the stratosphere, long-term surface temperatures on these exoplanets would have to be more than 66 °C (150 °F) higher than what we experience here on Earth.

These temperatures could create powerful convective storms on the surface. However, these storms could not be the reason water reaches the stratosphere when it comes to slowly rotating planets entering a moist greenhouse state – where water vapor intensifies heat. Planets that orbit closely to their parent stars are known to either have a slow rotation or to be tidally-locked with their planets, thus making convective storms unlikely.

This occurs quite often for terrestrial planets that are located around low-mass, ultra cool, M-type (red dwarf) stars. For these planets, their proximity to their host star means that it’s gravitational influence will be strong enough to slow down or completely arrest their rotation. When this occurs, thick clouds form on the dayside of the planet, protecting it from much of the star’s light.

The team found that, while this could keep the dayside cool and prevent water vapor from rising, the amount of near-Infrared radiation (NIR) could provide enough heat to cause a planet to enter a moist greenhouse state. This is especially true of M-type and other cool dwarf stars, which are known to produce more in the way of NIR. As this radiation warms the clouds, water vapor will rise into the stratosphere.

Artist’s impression of Proxima b, the closest exoplanet to the Solar System. In the background, the binary system of Alpha Centauri can be seen. Credit: ESO/M. Kornmesser

To address this, Fujii and her team relied on three-dimensional general circulation models (GCMs) which incorporate atmospheric circulation and climate heterogeneity. For the sake of their model, the team started with a planet that had an Earth-like atmosphere and was entirely covered by oceans. This allowed the team to clearly see how variations in distance from different types of stars would effect conditions on the planets surfaces.

These assumptions allowed the team to clearly see how changing the orbital distance and type of stellar radiation affected the amount of water vapor in the stratosphere. As Dr. Fujii explained in a NASA press release:

“Using a model that more realistically simulates atmospheric conditions, we discovered a new process that controls the habitability of exoplanets and will guide us in identifying candidates for further study… We found an important role for the type of radiation a star emits and the effect it has on the atmospheric circulation of an exoplanet in making the moist greenhouse state.”

In the end, the team’s new model demonstrated that since low-mass star emit the bulk of their light at NIR wavelengths, a moist greenhouse state will result for planets orbiting closely to them. This would result in conditions on their surfaces that comparable to what Earth experiences in the tropics, where conditions are hot and moist, instead of hot and dry.

Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO

What’s more, their model indicated that NIR-driven processes increased moisture in the stratosphere gradually, to the point that exoplanets orbiting closer to their stars could remain habitable. This new approach to assessing potential habitability will allow astronomers to simulate circulation of planetary atmospheres and the special features of that circulation, which is something one-dimensional models cannot do.

In the future, the team plans to assess how variations in planetary characteristics -such as gravity, size, atmospheric composition, and surface pressure – could affect water vapor circulation and habitability. This will, along with their 3-dimensional model that takes planetary circulation patterns into account, allow astronomers to determine the potential habitability of distant planets with greater accuracy. As Anthony Del Genio indicated:

“As long as we know the temperature of the star, we can estimate whether planets close to their stars have the potential to be in the moist greenhouse state. Current technology will be pushed to the limit to detect small amounts of water vapor in an exoplanet’s atmosphere. If there is enough water to be detected, it probably means that planet is in the moist greenhouse state.”

Beyond offering astronomers a more comprehensive method for determining exoplanet habitability, this study is also good news for exoplanet-hunters hoping to find habitable planets around M-type stars. Low-mass, ultra-cool, M-type stars are the most common star in the Universe, accounting for roughly 75% of all stars in the Milky Way. Knowing that they could support habitable exoplanets greatly increases the odds of find one.

Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech
Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech

In addition, this study is VERY good news given the recent spate of research that has cast serious doubt on the ability of M-type stars to host habitable planets. This research was conducted in response to the many terrestrial planets that have been discovered around nearby red dwarfs in recent years. What they revealed was that, in general, red dwarf stars experience too much flare and could strip their respective planets of their atmospheres.

These include the 7-planet TRAPPIST-1 system (three of which are located in the star’s habitable zone) and the closest exoplanet to the Solar System, Proxima b. The sheer number of Earth-like planets discovered around M-type stars, coupled with this class of star’s natural longevity, has led many in the astrophysical community to venture that red dwarf stars might be the most likely place to find habitable exoplanets.

With this latest study, which indicates that these planets could be habitable after all, it would seem that the ball is effectively back in their court!

Further Reading: NASA, The Astrophysical Journal

 

Sky Pointing Curiosity Captures Breathtaking Vista of Mount Sharp and Crater Rim, Climbs Vera Rubin Seeking Hydrated Martian Minerals

NASA’s Curiosity rover raised robotic arm with drill pointed skyward while exploring Vera Rubin Ridge at the base of Mount Sharp inside Gale Crater - backdropped by distant crater rim. This navcam camera mosaic was stitched from raw images taken on Sol 1833, Oct. 2, 2017 and colorized. Credit: NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo
NASA’s Curiosity rover raised robotic arm with drill pointed skyward while exploring Vera Rubin Ridge at the base of Mount Sharp inside Gale Crater – backdropped by distant crater rim. This navcam camera mosaic was stitched from raw images taken on Sol 1833, Oct. 2, 2017 and colorized. Credit: NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo

5 years after a heart throbbing Martian touchdown, Curiosity is climbing Vera Rubin Ridge in search of “aqueous minerals” and “clays” for clues to possible past life while capturing “truly breathtaking” vistas of humongous Mount Sharp – her primary destination – and the stark eroded rim of the Gale Crater landing zone from ever higher elevations, NASA scientists tell Universe Today in a new mission update.

“Curiosity is doing well, over five years into the mission,” Michael Meyer, NASA Lead Scientist, Mars Exploration Program, NASA Headquarters told Universe Today in an interview.

“A key finding is the discovery of an extended period of habitability on ancient Mars.”

The car-sized rover soft landed on Mars inside Gale Crater on August 6, 2012 using the ingenious and never before tried “sky crane” system.

A rare glimpse of Curiosity’s arm and turret mounted skyward pointing drill is illustrated with our lead mosaic from Sol 1833 of the robot’s life on Mars – showing a panoramic view around the alien terrain from her current location in October 2017 while actively at work analyzing soil samples.

“Your mosaic is absolutely gorgeous!’ Jim Green, NASA Director Planetary Science Division, NASA Headquarters, Washington D.C., told Universe Today

“We are at such a height on Mt Sharp to see the rim of Gale Crater and the top of the mountain. Truly breathtaking.”

The rover has ascended more than 300 meters in elevation over the past 5 years of exploration and discovery from the crater floor to the mountain ridge. She is driving to the top of Vera Rubin Ridge at this moment and always on the lookout for research worthy targets of opportunity.

Additionally, the Sol 1833 Vera Rubin Ridge mosaic, stitched by the imaging team of Ken Kremer and Marco Di Lorenzo, shows portions of the trek ahead to the priceless scientific bounty of aqueous mineral signatures detected by spectrometers years earlier from orbit by NASA’s fleet of Red Planet orbiters.

NASA’s Curiosity rover as seen simultaneously on Mars surface and from orbit on Sol 1717, June 5, 2017. The robot snapped this self portrait mosaic view while approaching Vera Rubin Ridge at the base of Mount Sharp inside Gale Crater – backdropped by distant crater rim. This navcam camera mosaic was stitched from raw images and colorized. Inset shows overhead orbital view of Curiosity (blue feature) amid rocky mountainside terrain taken the same day by NASA’s Mars Reconnaissance Orbiter. Credit: NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo

“Curiosity is on Vera Rubin Ridge (aka Hematite Ridge) – it is the first aqueous mineral signature that we have seen from space, a driver for selecting Gale Crater,” NASA HQ Mars Lead Scientist Meyer elaborated.

“And now we have access to it.”

The Sol 1833 photomosaic illustrates Curiosity maneuvering her 7 foot long (2 meter) robotic arm during a period when she was processing and delivering a sample of the “Ogunquit Beach” for drop off to the inlet of the CheMin instrument earlier in October. The “Ogunquit Beach” sample is dune material that was collected at Bagnold Dune II this past spring.

The sample drop is significant because the drill has not been operational for some time.

“Ogunquit Beach” sediment materials were successfully delivered to the CheMin and SAM instruments over the following sols and multiple analyses are in progress.

To date three CheMin integrations of “Ogunquit Beach” have been completed. Each one brings the mineralogy into sharper focus.

Researchers used the Mastcam on NASA’s Curiosity Mars rover to gain this detailed view of layers in “Vera Rubin Ridge” from just below the ridge. The scene combines 70 images taken with the Mastcam’s right-eye, telephoto-lens camera, on Aug. 13, 2017.
Credit: NASA/JPL-Caltech/MSSS

What’s the status of the rover health at 5 years, the wheels and the drill?

“All the instruments are doing great and the wheels are holding up,” Meyer explained.

“When 3 grousers break, 60% life has been used – this has not happened yet and they are being periodically monitored. The one exception is the drill feed (see detailed update below).”

NASA’s Curiosity rover explores sand dunes inside Gale Crater with Mount Sharp in view on Mars on Sol 1611, Feb. 16, 2017, in this navcam camera mosaic, stitched from raw images and colorized. Credit: NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo

NASA’s 1 ton Curiosity Mars Science Laboratory (MSL) rover is now closer than ever to the mineral signatures that were the key reason why Mount Sharp was chosen as the robots landing site years ago by the scientists leading the unprecedented mission.

Along the way from the ‘Bradbury Landing’ zone to Mount Sharp, six wheeled Curiosity has often been climbing. To date she has gained over 313 meters (1027 feet) in elevation – from minus 4490 meters to minus 4177 meters today, Oct. 19, 2017, said Meyer.

The low point was inside Yellowknife Bay at approx. minus 4521 meters.

VRR alone stands about 20 stories tall and gains Curiosity approx. 65 meters (213 feet) of elevation to the top of the ridge. Overall the VRR traverse is estimated by NASA to take drives totaling more than a third of a mile (570 m).

Curiosity images Vera Rubin Ridge during approach backdropped by Mount Sharp. This navcam camera mosaic was stitched from raw images taken on Sol 1726, June 14, 2017 and colorized. Credit: NASA/JPL/Marco Di Lorenzo/Ken Kremer/kenkremer.com

“Vera Rubin Ridge” or VRR is also called “Hematite Ridge.” It’s a narrow and winding ridge located on the northwestern flank of Mount Sharp. It was informally named earlier this year in honor of pioneering astrophysicist Vera Rubin.

The intrepid robot reached the base of the ridge in early September.

The ridge possesses steep cliffs exposing stratifications of large vertical sedimentary rock layers and fracture filling mineral deposits, including the iron-oxide mineral hematite, with extensive bright veins.

VRR resists erosion better than the less-steep portions of the mountain below and above it, say mission scientists.

Curiosity rover raises robotic arm high while scouting the Bagnold Dune Field and observing dust devils inside Gale Crater on Mars on Sol 1625, Mar. 2, 2017, in this navcam camera mosaic stitched from raw images and colorized. Note: Wheel tracks at right, distant crater rim in background. Credit: NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo

What’s ahead for Curiosity in the coming weeks and months exploring VRR before moving onward and upwards to higher elevation?

“Over the next several months, Curiosity will explore Vera Rubin Ridge,” Meyer replied.

“This will be a big opportunity to ground-truth orbital observations. Of interest, so far, the hematite of VRR does not look that different from what we have been seeing all along the Murray formation. So, big question is why?”

“The view from VRR also provides better access to what’s ahead in exploring the next aqueous mineral feature – the clay, or phyllosilicates, which can be indicators of specific environments, putting constraints on variables such as pH and temperature,” Meyer explained.

The clay minerals or phyllosilicates form in more neutral water, and are thus extremely scientifically interesting since pH neutral water is more conducive to the origin and evolution of Martian microbial life forms, if they ever existed.

How far away are the clays ahead and when might Curiosity reach them?

“As the crow flies, the clays are about 0.5 km,” Meyer replied. “However, the actual odometer distance and whether the clays are where we think they are – area vs. a particular location – can add a fair degree of variability.”

The clay rich area is located beyond the ridge.

Over the past few months Curiosity make rapid progress towards the hematite-bearing location of Vera Rubin Ridge after conducting in-depth exploration of the Bagnold Dunes earlier this year.

“Vera Rubin Ridge is a high-standing unit that runs parallel to and along the eastern side of the Bagnold Dunes,” said Mark Salvatore, an MSL Participating Scientist and a faculty member at Northern Arizona University, in a mission update.

“From orbit, Vera Rubin Ridge has been shown to exhibit signatures of hematite, an oxidized iron phase whose presence can help us to better understand the environmental conditions present when this mineral assemblage formed.”

Curiosity is using the science instruments on the mast, deck and robotic arm turret to gather detailed research measurements with the cameras and spectrometers. The pair of miniaturized chemistry lab instruments inside the belly – CheMin and SAM – are used to analyze the chemical and elemental composition of pulverized rock and soil gathered by drilling and scooping selected targets during the traverse.

A key instrument is the drill which has not been operational. I asked Meyer for a drill update.

“The drill feed developed problems retracting (two stabilizer prongs on either side of the drill retract, controlling the rate of drill penetration),” Meyer replied.

“Because the root cause has not been found (think FOD) and the concern about the situation getting worse, the drill feed has been retracted and the engineers are working on drilling without the stabilizing prongs.”

“Note, a consequence is that you can still drill and collect sample but a) there is added concern about getting the drill stuck and b) a new method of delivering sample needs to be developed and tested (the drill feed normally needs to be moved to move the sample into the chimera). One option that looks viable is reversing the drill – it does work and they are working on the scripts and how to control sample size.”

Ascending and diligently exploring the sedimentary lower layers of Mount Sharp, which towers 3.4 miles (5.5 kilometers) into the Martian sky, is the primary destination and goal of the rover’s long term scientific expedition on the Red Planet.

“Lower Mount Sharp was chosen as a destination for the Curiosity mission because the layers of the mountain offer exposures of rocks that record environmental conditions from different times in the early history of the Red Planet. Curiosity has found evidence for ancient wet environments that offered conditions favorable for microbial life, if Mars has ever hosted life,” says NASA.

Stay tuned. In part 2 we’ll discuss the key findings from Curiosity’s first 5 years exploring the Red Planet.

As of today, Sol 1850, Oct. 19, 2017, Curiosity has driven over 10.89 miles (17.53 kilometers) since its August 2012 landing inside Gale Crater from the landing site to the ridge, and taken over 445,000 amazing images.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

Map shows route driven by NASA’s Mars rover Curiosity through Sol 1827 of the rover’s mission on Mars (September 27, 2017). Numbering of the dots along the line indicate the sol number of each drive. North is up. Since touching down in Bradbury Landing in August 2012, Curiosity has driven 10.84 miles (17.45 kilometers). The base image from the map is from the High Resolution Imaging Science Experiment Camera (HiRISE) in NASA’s Mars Reconnaissance Orbiter. Credit: NASA/JPL/UA
Curiosity’s Traverse Map Through Sol 1717. This map shows the route driven by NASA’s Mars rover Curiosity through the 1717 Martian day, or sol, of the rover’s mission on Mars (June 05, 2017). The base image from the map is from the High Resolution Imaging Science Experiment Camera (HiRISE) in NASA’s Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/Univ. of Arizona

Nope, our Temporary Moon Isn’t Space Junk, it’s an Asteroid

Mining asteroids might be necessary for humanity to expand into the Solar System. But what effect would asteroid mining have on the world's economy? Credit: ESA.

In April of 2016, astronomers became aware of a distant object that appeared to be orbiting the Sun, but was also passing close enough to Earth that it could be periodically viewed using the most powerful telescopes. Since then, there has been ample speculation as to what this “Temporary Moon” could be, with most astronomers claiming that it is likely nothing more than an asteroid.

However, some suggested that it was a burnt-out rocket booster trapped in a near-Earth orbit. But thanks to new study by a team from the University of Arizona’s Lunar and Planetary Laboratory, this object – known as (469219) 2016 HO3 – has been confirmed as an asteroid. While this small near-Earth-asteroid orbits the Sun, it also orbits Earth as a sort of “quasi-satellite”.

The team that made this discovery was led by Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory. Their research was also made possible thanks to NASA’s Near-Earth Object Observations Program. This program is maintained by NASA’s Center for Near-Earth Object Studies (CNEOS) and provides grants to institutions dedicated to the research of NEOs.

2016 HO3 is an asteroid that appears to orbit around Earth due to the mechanics of its peculiar orbit around the sun. Credit: NASA-JPL

The details of this discovery were presented this week at the 49th Annual Meeting of the Division for Planetary Sciences in Utah at a presentation titled “Ground-based Characterization of Earth Quasi Satellite (469219) 2016 HO3”. During the course of the presentation, Reddy and his colleagues described how they spotted the object using the Large Binocular Telescope (LBT) at the LBT Observatory on Mount Graham in southeastern Arizona.

According to their observations, 2016 HO3 measures just 100 meters (330 feet) across and is the most stable quasi-satellite discovered to date (of which there have been five). Over the course of a few centuries, this asteroid remains at a distance of 38 to 100 lunar distances – i.e. the distance between the Earth and the Moon. As Reddy explained in a UANews press statement, this makes the asteroid a challenging target:

“While HO3 is close to the Earth, its small size – possibly not larger than 100 feet – makes it challenging target to study. Our observations show that HO3 rotates once every 28 minutes and is made of materials similar to asteroids.”

Discovering the true nature of this object has also solved another big question – namely, where did 2016 HO3 come from? For those speculating that it might be space junk, it then became necessary to determine what the likely source of that junk was. Was it a remnant of an Apollo-era mission, or something else entirely? By determining that it is actually an NEO, Reddy and his team have indicted that it likely comes from the same place as other NEOs.

Vishnu Reddy of the University of Arizona’s Lunar Planetary Laboratory. Credit: Bob Demers/UANews

Reddy and his colleagues also indicated that 2016 HO3 reflected light off its surface in a way that is similar to meteorites that have been studied here on Earth. This was another indication that 2016 HO3 has similar origins to other NEOs (some of which have entered our atmosphere as meteors) which are generally asteroids that were kicked out of the Main Belt by Jupiter’s gravity.

“In an effort to constrain its rotation period and surface composition, we observed 2016 HO3 on April 14 and 18 with the Large Binocular Telescope and the Discovery Channel Telescope,” Reddy said. “The derived rotation period and the spectrum of emitted light are not uncommon among small NEOs, suggesting that 2016 HO3 is a natural object of similar provenance to other small NEOs.”

But unlike other NEOs which periodically cross Earth’s orbit, “quasi-satellites” are distinguished by their rather unique orbits. In the case of 2016 HO3, it has an orbit that follows a similar path to that the Earth’s; but because it is not dominated by the Earth’s gravity, their two orbits are out of sync. This causes 2016 HO3 to make annual loops around the Earth as it orbits the Sun.

Artist’s impression of a hypothetical astronaut mission to an asteroid. Credit: NASA Human Exploration Framework Team

Christian Veillet, one of co-authors of the presentation, is also the director of the LBT Observatory. As he explained, this characteristic could make “quasi-satellites” ideal targets for future NEO studies:

“Of the near-Earth objects we know of, these types of objects would be the easiest to reach, so they could potentially make suitable targets for exploration. With its binocular arrangement of two 8.4-meter mirrors, coupled with a very efficient pair of imagers and spectrographs like MODS, LBT is ideally suited to the characterization of these Earth’s companions.”

Similarly, their orbital characteristic could make “quasi-satellites” an ideal target for future space missions. One of NASA’s main goals in the coming decade is to send a crewed mission to a Near-Earth Object in order to test the Orion spacecraft and the Space Launch System. Such a mission would also help develop the necessary expertise for mounting missions deeper into space (i.e. to Mars and beyond).

The study of Near-Earth Objects is also of immense importance when it comes to determining how and where as asteroid might pose a threat to Earth. This knowledge allows for advanced warnings which can potentially save lives. It is also significant when it comes to the development of proposed counter-measures, several of which are currently being explored.

And be sure to enjoy this video of 2016 HO3’s orbit, courtesy of NASA’s Jet Propulsion Laboratory:

Further Reading: UANews