Posted on by Matt Williams

Could There be Alien Life Right Beneath the Surface of Icy Worlds Like Enceladus and Europa?

The moons of Europa and Enceladus, as imaged by the Galileo and Cassini spacecraft. Credit: NASA/ESA/JPL-Caltech/SETI Institute

For decades, scientists have been speculating that life could exist in beneath the icy surface of Jupiter’s moon Europa. Thanks to more recent missions (like the Cassini spacecraft), other moons and bodies have been added to this list as well – including Titan, Enceladus, Dione, Triton, Ceres and Pluto. In all cases, it is believed that this life would exist in interior oceans, most likely around hydrorthermal vents located at the core-mantle boundary.

One problem with this theory is that in such undersea environments, life might have a hard time getting some of the key ingredients it would need to thrive. However, in a recent study – which was supported by the NASA Astrobiology Institute (NAI) – a team of researchers ventured that in the outer Solar System, the combination of high-radiation environments, interior oceans and hydrothermal activity could be a recipe for life.

The study, titled “The Possible Emergence of Life and Differentiation of a Shallow Biosphere on Irradiated Icy Worlds: The Example of Europa“, recently appeared in the scientific journal Astrobiology. The study was led by Dr. Michael Russell with the support of Alison Murray of the Desert Research Institute and Kevin Hand – also a researcher with NASA JPL.

Vestimentiferan tubeworms (Riftia pachyptila) found near the Galapagos islands. Credit: NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011.

For the sake of their study, Dr. Russell and his colleagues considered how the interaction between alkaline hydrothermal springs and sea water is often considered to be how the key building blocks for life emerged here on Earth. However, they emphasize that this process was also dependent on energy provided by our Sun. The same process could have happened on moon’s like Europa, but in a different way. As they state in their paper:

“[T]he significance of the proton and electron flux must also be appreciated, since those processes are at the root of life’s role in free energy transfer and transformation. Here, we suggest that life may have emerged on irradiated icy worlds such as Europa, in part as a result of the chemistry available within the ice shell, and that it may be sustained still, immediately beneath that shell.”

In the case of moon’s like Europa, hydrothermal springs would be responsible for churning up all the necessary energy and ingredients for organic chemistry to take place. Ionic gradients, such as oxyhydroxides and sulfides, could drive the key chemical processes – where carbon dioxide and methane are hydrogenated and oxidized, respectively – which could lead to the creation of early microbial life and nutrients.

At the same time, the heat from hydrothermal vents would push these microbes and nutrients upwards towards the icy crust. This crust is regularly bombarded by high-energy electrons created by Jupiter’s powerful magnetic field, a process which creates oxidants. As scientists have known for some time from surveying Europa’s crust, there is a process of exchange between the moon’s interior ocean and its surface.

Artist’s concept of plume activity on the surface of Europa. Credit: NASA/JPL-Caltech

As Dr. Russell and his colleagues indicate, this action would most likely involve the plume activity that has been observed on Europa’s surface, and could lead to a network of ecosystems on the underside of Europa’s icy crust:

“Models for transport of material within Europa’s ocean indicate that hydrothermal plumes could be well constrained within the ocean (primarily by the Coriolis force and thermal gradients), leading to effective delivery through the ocean to the ice-water interface. Organisms fortuitously transported from hydrothermal systems to the ice-water interface along with unspent fuels could potentially access a larger abundance of oxidants directly from the ice. Importantly, oxidants might only be available where the ice surface has been driven to the base of the ice shell.”

As Dr. Russel indicated in an interview with Astrobiology Magazine, microbes on Europa could reach densities similar to what has been observed around hydrothermal vents here on Earth, and may bolster the theory that life on Earth also emerged around such vents. “All the ingredients and free energy required for  life are all focused in one place,” he said. “If we were to find life on Europa, then that would strongly support the submarine alkaline vent theory.”

This study is also significant when it comes to mounting future missions to Europa. If microbial ecosystems exist on the undersides of Europa’s icy crust, then they could be explored by robots that are able to penetrate the surface, ideally by traveling down a plume tunnel. Alternately, a lander could simply position itself near an active plume and search for signs of oxidants and microbes coming up from the interior.

Artist’s impression of a hypothetical ocean cryobot (a robot capable of penetrating water ice) in Europa. Credit: NASA

Similar missions could also be mounted to Enceladus, where the presence of hydrothermal vents has already been confirmed thanks to the extensive plume activity observed around its southern polar region. Here too, a robotic tunneler could enter surface fissures and explore the interior to see if ecosystems exist on the underside of the moon’s icy crust. Or a lander could position itself near the plumes and examine what is being ejected.

Such missions would be simpler and less likely to cause contamination than robotic submarines designed to explore Europa’s deep ocean environment. But regardless of what form a future mission to Europa, Enceladus, or other such bodies takes, it is encouraging to know that any life that may exist there could be accessible. And if these missions can sniff it out, we will finally know that life in the Solar System evolved in places other than Earth!

Further Reading: Astrobiology Magazine, Astrobiology

Posted on by Matt Williams

Jupiter’s Atmospheric Bands Go Surprisingly Deep

Jupiter's colorful stripes are cloud belts that extend thousand of kilometers deep. NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

For centuries, astronomers have been observing Jupiter swirling surface and been awed and mystified by its appearance. The mystery only deepened when, in 1995, the Galileo spacecraft reached Jupiter and began studying its atmosphere in depth. Since that time, astronomers have puzzled over its colored bands and wondered if they are just surface phenomenon, or something that goes deeper.

Thanks to the Juno spacecraft, which has been orbiting Jupiter since July of 2016, scientists are now much closer to answering that question. This past week, three new studies were published based on Juno data that presented new findings on Jupiter’s magnetic field, its interior rotation, and how deep its belts extend. All of these findings are revising what scientists think of Jupiter’s atmosphere and its inner layers.

The studies were titled “Measurement of Jupiter’s asymmetric gravity field“, “Jupiter’s atmospheric jet streams extend thousands of kilometres deep” and “A suppression of differential rotation in Jupiter’s deep interior“, all of which were published in Nature on March 7th, 2018. The studies were led by Prof. Luciano Iess of Sapienza University of Rome, the second by Prof. Yohai Kaspi and Dr. Eli Galanti of the Weizmann Institute of Science, and the third by Prof. Tristan Guillot of the Observatoire de la Cote d’Azur.

Jupiter’s South Pole, taken during a Juno flyby on Dec 16th, 2017. Credit: NASA/JPL-Caltech/SwRI/MSSS/David Marriott

The research effort was led by Professo Kaspi and Dr. Galanti, who in addition to being the lead authors on the second study were co-authors on the other two. The pair have been preparing for this analysis even before Juno launched in 2011, during which time they built mathematical tools to analyze the gravitational field data and get a better grasp of Jupiter’s atmosphere and its dynamics.

All three studies were based on data gathered by Juno as it passed from one of Jupiter’s pole to the other every 53-days – a maneuver known as a “perijove”. With each pass, the probe used its advanced suite of instruments to peer beneath the surface layers of the atmosphere. In addition, radio waves emitted by the probe were measured to determine how they were shifted by the planet’s gravitational field with each orbit.

As astronomers have understood for some time, Jupiter’s jets flow in bands from east to west and west to east. In the process, they disrupt the even distribution of mass on the planet. By measuring changes in the planet’s gravity field (and thus this mass imbalance), Dr. Kaspi and Dr. Galanti’s analytical tools were able to calculate how deep the storms extend beneath the surface and what it’s interior dynamics are like.

Above all, the team expected to find anomalies because of the way the planet deviates from being a perfect sphere – which is due to how its rapid rotation squishes it slightly. However, they also looked for additional anomalies that could be explained due to the presence of powerful winds in the atmosphere.

This image from Juno’s JunoCam captured the south pole in visible light only. It’s a puzzle why the north and south poles are so similar, yet have a different number of cyclones. Image: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles

In the first study, Dr. Iess and his colleagues used precise Doppler tracking of the Juno spacecraft to conduct measurements of Jupiter’s gravity harmonics – both even and odd. What they determined was Jupiter’s magnetic field has a north-south asymmetry, which is indicative of interior flows in the atmosphere.

Analysis of this asymmetry was followed-up on in the second study, where Dr. Kaspi, Dr. Galanti and their colleagues used the variations in the planet’s gravity field to calculate the depth of Jupiter’s east-west jet streams. By measuring how these jets cause an imbalance in Jupiter’s gravity field, and even disrupt the mass of the planet, they concluded that they extend to a depth of 3000 km (1864 mi).

From all this, Prof. Guillot and his colleagues conducted the third study, where they used the previous findings about the planet’s gravitational field and jet streams and compared the results to predictions of interior models. From this, they determined that the interior of the planet rotates almost like a rigid body and that differential rotation decreases farther down.

In addition, they found that the zones of atmospheric flow extended to between 2,000 km (1243 mi) and 3,500 km (2175 mi) deep, which was consistent with the constraints obtained from the odd gravitational harmonics. This depth also corresponds to the point where electric conductivity would become large enough that magnetic drag would suppress differential rotation.

Based on their findings, the team also calculated that Jupiter’s atmosphere constitutes 1% of its total mass. For comparison, Earth’s atmosphere is less than a millionth of its total mass. Still, as Dr. Kaspi explained in Weizzmann Institute press release, this was rather surprising:

“That is much more than anyone thought and more than what has been known from other planets in the Solar System. That is basically a mass equal to three Earths moving at speeds of tens of meters per second.”

All told, these studies have shed new light on the Jupiter’s atmospheric dynamics and interior structure. At present, the subject of what resides at Jupiter’s core remains unresolved. But the researchers hope to analyze further measurements made by Juno to see whether Jupiter has a solid core and (if so) to determine its mass. This in turn will help astronomers learn a great deal about the Solar System’s history and formation.

In addition, Kaspi and Galanti are looking to use some of the same methods they developed to characterize Jupiter’s jet streams to tackle its most iconic feature – Jupiter’s Great Red Spot. In addition to determining how deep this storm extends, they also hope to learn why this storm has persisted for so many centuries, and why it has been noticeably shrinking in recent years.

The Juno mission is expected to wrap up in July of 2018. Barring any extensions, the probe will conduct a controlled deorbit into Jupiter’s atmosphere after conducting perijove 14. However, even after the mission is over, scientists will be analyzing the data it has collected for years to come. What this reveals about the Solar System’s largest planet will also go a long way towards informing out understanding of the Solar System.

Further Reading: Weizmann Institute of Science, Nature, Nature (2), Nature (3),

Posted on by Matt Williams

Air-Breathing Electric Thruster Could Keep Satellites in Low Earth Orbit for Years

An ESA-led team has built and fired an electric thruster to ingest scarce air molecules from the top of the atmosphere as propellant, opening the way to satellites flying in very low orbits for years on end. Credit: ESA/Sitael

When it comes to the future of space exploration, one of the greatest challenges is coming up with engines that can maximize performance while also ensuring fuel efficiency. This will not only reduce the cost of individual missions, it will ensure that robotic spacecraft (and even crewed spacecraft) can operate for extended periods of time in space without having to refuel.

In recent years, this challenge has led to some truly innovative concepts, one of which was recently build and tested for the very first time by an ESA team. This engine concept consists of an electric thruster that is capable of “scooping” scarce air molecules from the tops of atmospheres and using them as propellant. This development will open the way for all kinds of satellites that can operate in very low orbits around planets for years at a time.

The concept of an air-breathing thruster (aka. Ram-Electric Propulsion) is relatively simple. In short, the engine works on the same principles as a ramscoop (where interstellar hydrogen is collected to provide fuel) and an ion engine – where collected particles are charged and ejected. Such an engine would do away with onboard propellant by taking in atmospheric molecules as it passed through the top of a planet’s atmosphere.

The test set-up for the air-breathing electric propulsion thruster recently developed by Sitael and QuinteScience in conjunction with the ESA. Credit: ESA/Sitael

The concept was the subject of a study titled “RAM Electric Propulsion for Low Earth Orbit Operation: An ESA Study“, which was presented at the 30th International Electric Propulsion Conference in 2007. The study emphasized how “Low Earth orbit satellites are subject to atmospheric drag and thus their lifetimes are limited with current propulsion technologies by the amount of propellant they can carry to compensate for it.”

The study’s authors also indicated how satellites using high specific impulse electric propulsion would be capable of compensating for drag during low altitude operation for an extended period of time. But as they conclude, such a mission would also be limited to the amount of fuel it could carry. This was certainly the case for the ESA’s Gravity field and steady-state Ocean Circulation Explorer (GOCE) gravity-mapper satellite,

While GOCE remained in orbit of Earth for more than four years and operated at altitudes as low as 250 km (155 mi), its mission ended the moment it exhausted its 40 kg (88 lbs) supply of xenon as propellant. As such, the concept of an electric propulsion system that an utilize atmospheric molecules as propellant has also been investigated. As Dr. Louis Walpot of the ESA explained in an ESA press release:

“This project began with a novel design to scoop up air molecules as propellant from the top of Earth’s atmosphere at around 200 km altitude with a typical speed of 7.8 km/s.”

Diagram illustrated how air-breathing electric propulsion works. Credit: ESA–A. Di Giacomo

To develop this concept, the Italian aerospace company Sitael and the Polish aerospace company QuinteScience teamed up to create a novel intake and thruster design. Whereas QuinteScience built an intake that would collect and compress incoming atmospheric particles, Sitael developed a dual-stage thruster that would charge and accelerate these particles to generate thrust.

The team then ran computer simulations to see how particles would behave across a range of intake options. But in the end, they chose to conduct a practice test to see if the combined intake and thruster would work together or not. To do this, the team tested it in a vacuum chamber at one of Sitael’s test facilities. The chamber simulated an environment at 200 km altitude while a “particle flow generator” provided the oncoming high-speed molecules.

To provide a more complete test and make sure the thruster would function in a low-pressure environment, the team began by igniting it with xenon-propellant. As Dr. Walpot explained:

“Instead of simply measuring the resulting density at the collector to check the intake design, we decided to attach an electric thruster. In this way, we proved that we could indeed collect and compress the air molecules to a level where thruster ignition could take place, and measure the actual thrust. At first we checked our thruster could be ignited repeatedly with xenon gathered from the particle beam generator.”

Fired at first using standard xenon propellant, the test thruster was then shifted to atmospheric air, proving the principle of air-breathing electric propulsion. Credit: ESA

As a next step, the team partially replace xenon with a nitrogen-oxygen air mixture to simulate Earth’s upper atmosphere. As hoped, the engine kept firing, and the only thing that changed was the color of the thrust.

“When the xenon-based blue color of the engine plume changed to purple, we knew we’d succeeded,” said Dr. Walpot. “The system was finally ignited repeatedly solely with atmospheric propellant to prove the concept’s feasibility. This result means air-breathing electric propulsion is no longer simply a theory but a tangible, working concept, ready to be developed, to serve one day as the basis of a new class of missions.”

The development of air-breathing electric thrusters could allow for an entirely new class of satellite that could operate with the fringes of Mars’, Titan’s and other bodies atmospheres for years at a time. With this kind of operational lifespan, these satellites could gather volumes of data on these bodies’ meteorological conditions, seasonal changes, and the history of their climates.

Such satellites would also be very useful when it comes to observing Earth. Since they would be able to operate at lower altitudes than previous missions, and would not be limited by the amount of propellant they could carry, satellites equipped with air-breathing thrusters could operate for extended periods of time. As a result, they could offer more in-depth analyses on Climate Change, and monitor meteorological patterns, geological changes, and natural disasters more closely.

Further Reading: ESA

Posted on by Evan Gough

Gaze in Wonder at Jupiter’s Mysterious Geometric Polar Storms

This wondrous image of Jupiter's south pole shows the arrangement of cyclones that is unique in our Solar System: five circumpolar cyclones perfectly arranged around a single polar cyclone. Image: NASA/SWRI/JPL/ASI/INAF/IAPS

When the Juno spacecraft arrived at Jupiter in July 2016, it quickly got to work. Among the multitude of stunning images of the planet were our first ever images of Jupiter’s poles. And what we saw there was a huge surprise: geometric arrangements of cyclones in persistent patterns.

Jupiter’s polar regions have always been a mystery to Earth-bound observers. The planet isn’t tilted much, which means the poles are always tantalizingly out of view. Other spacecraft visiting Jupiter have focused on the equatorial regions, but Juno’s circumpolar orbit is giving us good, close-up views of Jupiter’s poles.

“They are extraordinarily stable arrangements of such chaotic elements. We’d never seen anything like it.” – Morgan O’Neill, University of Chicago

Juno has a whole suite of instruments designed to unlock some of the mysteries surrounding Jupiter, including an infrared imager and a visible light camera. The polar regions are a particular focus for the mission, and astronomers were looking forward to their first views of Jupiter’s hidden poles. They were not disappointed when they got them.

Each of Jupiter’s poles is a geometric array of large cyclones arranged in persistent, polygonal patterns. At the north pole, eight storms are arranged around a single polar cyclone. In the south, one storm is encircled by five others.

Jupiter’s north pole is an arrangement of 8 cyclones around one central cyclone. Image: NASA/SWRI/JPL/ASI/INAF/IAPS

This was a stunning discovery, and quickly led to questions around the why and the how of these storm arrangements. Jupiter’s atmosphere is dominated by storm activity, including the well-known horizontal storm bands in the equatorial regions, and the famous Great Red Spot. But these almost artful arrangements of polar storms were something else.

The persistent arrangement of the storms is a puzzle. Our current understanding tells us that the storms should drift around and merge, but these storms do neither. They just turn in place.

A new paper published in Nature is looking deeper into these peculiar arrangements of storms. The paper is by scientists from an international group of institutions including the University of Chicago. It’s one of four papers dedicated to new observations from the Juno spacecraft.

One of the paper’s co-authors is Morgan O’Neill, a University of Chicago postdoctoral scholar. Remarking on the storms, she had this to say: “They are extraordinarily stable arrangements of such chaotic elements. We’d never seen anything like it.”

This image from Juno’s JunoCam captured the south pole in visible light only. It’s a puzzle why the north and south poles are so similar, yet have a different number of cyclones. Image: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles

The strange geometrical arrangement of Jupiter’s polar storms reminded O’Neill of something from the library of strange physical phenomena only observed under laboratory conditions. Back in the ’90s, scientists had used electrons to simulate a frictionless, turbulent 2-D fluid as it cools. In those conditions, they observed similar behaviour. Rather than merging like expected, small vortices clumped together and formed equally spaced arrays around a center. They called these arrays “vortex crystals.”

This could help explain what’s happening at Jupiter’s poles, but it’s too soon to be certain. “The next step is: Can you create a model that builds a virtual planet and predicts these flows?” O’Neill said. That’ll be the next step in understanding the phenomenon.

Maybe it’s not surprising that these delicate-looking storms at the poles are so persistent. After all, the Great Red Spot on Jupiter has been visible for over 200 years. Maybe Jupiter is just huge and stable.

But the polar cyclones still require an explanation. And whatever that explanation is, understanding what’s happening on Jupiter will help us understand other planets better.

Posted on by Evan Gough

Hubble Sees a Huge Dust Cloud Around a Newly Forming Star

Astronomers have used NASA's Hubble Space Telescope to uncover a vast, complex dust structure, about 150 billion miles across, enveloping the young star HR 4796A. Image:NASA/ESA/G. Schneider (Univ. of Arizona)

Younger stars have a cloud of dusty debris encircling them, called a circumstellar disk. This disk is material left over from the star’s formation, and it’s out of this material that planets form. But scientists using the Hubble have been studying an enormous dust structure some 150 billion miles across. Called an exo-ring, this newly imaged structure is much larger than a circumstellar disk, and the vast structure envelops the young star HR 4796A and its inner circumstellar disk.

Discovering a dust structure around a young star is not new, and the star in this new paper from Glenn Schneider of the University of Arizona is probably our most (and best) studied exoplanetary debris system. But Schneider’s paper, along with capturing this new enormous dust structure, seems to have uncovered some of the interplay between the bodies in the system that has previously been hidden.

Schneider used the Space Telescope Imaging Spectrograph (STIS) on the Hubble to study the system. The system’s inner disk was already well-known, but studying the larger structure has revealed more complexity.

The Hubble Space Telescope has imaged a vast, complex dust structure surrounding the star HR 4769A. The bright, inner ring is well-known to astronomers, but the huge dust structure surrounding the whole system is a new discovery. Image: NASA/ESA/G. Schneider (Univ. of Arizona)

The origin of this vast structure of dusty debris is likely collisions between newly forming planets within the smaller inner ring. Outward pressure from the star HR 4769A then propelled the dust outward into space. The star is 23 times more luminous than our Sun, so it has the necessary energy to send the dust such a great distance.

A press release from NASA describes this vast exo-ring structure as a “donut-shaped inner tube that got hit by a truck.” It extends much further in one direction than the other, and looks squashed on one side. The paper presents a couple possible causes for this asymmetric extension.

It could be a bow wave caused by the host star travelling through the interstellar medium. Or it could be under the gravitational influence of the star’s binary companion (HR 4796B), a red dwarf star located 54 billion miles from the primary star.

“The dust distribution is a telltale sign of how dynamically interactive the inner system containing the ring is'” – Glenn Schneider, University of Arizona, Tucson.

The asymmetrical nature of the vast exo-structure points to complex interactions between all of the stars and planets in the system. We’re accustomed to seeing the radiation pressure from the host star shape the gas and dust in a circumstellar disk, but this study presents us with a new level of complexity to account for. And studying this system may open a new window into how solar systems form over time.

Artist’s impression of circumstellar disk of debris around a distant star. These disk are common around younger stars, but the star in this study has a massive dust cloud that envelops and dwarfs the smaller, inner ring. Credit: NASA/JPL

“We cannot treat exoplanetary debris systems as simply being in isolation. Environmental effects, such as interactions with the interstellar medium and forces due to stellar companions, may have long-term implications for the evolution of such systems. The gross asymmetries of the outer dust field are telling us there are a lot of forces in play (beyond just host-star radiation pressure) that are moving the material around. We’ve seen effects like this in a few other systems, but here’s a case where we see a bunch of things going on at once,” Schneider further explained.

The paper suggests that the location and brightness of smaller rings within the larger dust structure places constraints on the masses and orbits of planets within the system, even when the planets themselves can’t be seen. But that will require more work to determine with any specificity.

This paper represents a refinement and advancement of the Hubble’s imaging capabilities. The paper’s author is hopeful that the same methods using in this study can be used on other similar systems to better understand these larger dust structures, how they form, and what role they play.

As he says in the paper’s conclusion, “With many, if not most, technical challenges now understood and addressed, this capability should be used to its fullest, prior to the end of the HST mission, to establish a legacy of the most robust images of high-priority exoplanetary debris systems as an enabling foundation for future investigations in exoplanetary systems science.”

Posted on by Matt Williams

A New Planetary System Has Been Found with Three Super Earths

Artist’s impression of a view from the HD 7924 planetary system looking back toward our sun, which would be easily visible to the naked eye. Since HD 7924 is in our northern sky, an observer looking back at the sun would see objects like the Southern Cross and the Magellanic Clouds close to our sun in their sky. Credit: Karen Termaura and BJ Fulton, UH IfA

As of March 1st, 2018, 3,741 exoplanets have been confirmed in 2,794 systems, with 622 systems having more than one planet. Most of the credit for these discoveries goes to the Kepler space telescope, which has discovered roughly 3500 planets and 4500 planetary candidates. In the wake of all these discoveries, the focus has shifted from pure discovery to research and characterization.

In this respect, planets detected using the Transit Method are especially valuable since they allow for the study of these planets in detail. For example, a team of astronomers recently discovered three Super-Earths orbiting a star known GJ 9827, which is located just 100 light years (30 parsecs) from Earth. The proximity of the star, and the fact that it is orbited by multiple Super-Earths, makes this system ideal for detailed exoplanet studies.

The study, titled “A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs“, recently appeared online. The study was led by Joseph E. Rodriguez of the Harvard-Smithsonian Center for Astrophysics and included members from The University of Texas at Austin, Columbia University, the Massachusetts Institute of Technology, and the NASA Exoplanet Science Institute.

Artistic design of the super-Earth GJ 625 b and its star, GJ625 (Gliese 625). Credit: Gabriel Pérez/SMM (IAC)

As with all Kepler discoveries, these planets were discovered using the Transit Method (aka. Transit Photometry), where stars are monitored for periodic dips of brightness. These dips are the result of exoplanets passing in front of the star (i.e. transiting) relative to the observer. While this method is ideal for placing constraints on the size and orbital periods of a planet, it can also allow for exoplanet characterization.

Basically, scientists are able to learn things about their atmospheres by measuring the spectra produced by the star’s light as it passes through the planet’s atmosphere. Combined with radial velocity measurements of the star, scientists can also place constraints on the planet’s mass and radius and can determine things about the planet’s interior structure.

For the sake of their study, the team analyzed data obtained by the K2 mission, which showed the presence of three Super-Earths around the star GJ 9827 (GJ 9827 b, c, and d). Since they initially submitted their research paper back in September of 2017, the presence of these planets has been confirmed by another team of astronomers. As Dr. Rodriguez told Universe Today via email:

“We detected three super-Earth sized planets orbiting in a very compact configuration. Specifically, the three planets have radii of 1.6, 1.2, and 2.1 times the radius of Earth and all orbit their host star within 6.2 days. We note that this system was independently discovered (simultaneously) by another team from Wesleyan University (Niraula et al. 2017).”

The super-Earth exoplanet 55 Cancri e, depicted with its star in this artist’s concept, likely has an atmosphere thicker than Earth’s but with ingredients that could be similar to those of Earth’s atmosphere. Credit: NASA/JPL

These three exoplanets are especially interesting because the larger of the two have radii that place them in the range between being rocky or gaseous. Few such exoplanets have been discovered so far, which makes these three a prime target for research. As Dr. Rodriguez explained:

“Super Earth sized planets are the most common type of planet we know of but we do not have one in our own solar system, limiting our ability to understand them. They are especially important because their radii span the rock to gas transition (as I discuss below in one of the other responses). Essentially, planets larger then 1.6 times the radius of the Earth are less dense and have thick hydrogen/helium atmospheres while planets smaller are very dense with little to no atmosphere.”

Another interesting thing about these super-Earths is how their short orbital periods – which are 1.2, 3.6 and 6.2 days, respectively – would result in fairly hot temperatures. In short, the team estimates that the three super-Earths experience surface temperatures of 1172 K (899 °C; 1650 °F), 811 K (538 °C; 1000 °F), and 680 K (407 °C; 764 °F), respectively.

By comparison, Venus – the hottest planet in the Solar System – experiences surface temperatures of 735 K (462 °C; 863 °F). So while temperatures on Venus are hot enough to melt lead, conditions on GJ 9827 b are almost hot enough to melt bronze.

The light curve obtained during Campaign 12 of the K2 mission of the GJ 9827 system. Credit: Rodriguez et al., 2018.

However, the most significant thing about this discovery is the opportunities it could provide for exoplanet characterization. At just 100 light-years from Earth, it will be relatively easy for the next-generation telescopes (such as the James Webb Space Telescope) to conduct studies of their atmospheres and provide a more detailed picture of this system of planets.

In addition, these three strange planets are all in the same system, which makes conducting observation campaigns that much easier. As Rodriguez concluded:

“The GJ 9827 system is unique because one planet is smaller than this cutoff, one planet is larger, and the third planet has a radius of ~1.6  times the radius of the Earth, right on that border. So in one system, we have planets that span this rock to gas transition. This is important because we can study the atmosphere’s of these planets, look for differences in the composition of their atmospheres and begin to understand why this transition occurs at 1.6 times the radius of the Earth. Since all three planets orbit the same star, the effect of the host star is kept constant in this “experiment”. Therefore, if these three planets in GJ 9827 were instead orbiting three separate stars, we would have to worry about how the host star is influencing or affecting the planet’s atmosphere. In the GJ 9827 system, we do not have to worry about this since they orbit the same star.”

Further Reading: CfA, arXiv

Posted on by Evan Gough

Rosetta’s 67P Is The Result Of A Collision Of Two Comets

The comet 67P/Churyumov-Gerasimenko, which was visited by Rosetta in 2014-15, certainly appears to be the result of a collision between two comets. A new study explains how and when the collision occurred. By ESA/Rosetta/OSIRIS - http://www.esa.int/spaceinimages/Images/2014/12/Colour_image_of_comet, CC BY-SA 3.0,

Ever since we’ve been able to get closer looks at comets in our Solar System, we’ve noticed something a little puzzling. Rather than being round, they’re mostly elongated or multi-lobed. This is certainly true of Comet 67P/Churyumov-Gerasimenko (67P or Chury for short.) A new paper from an international team coordinated by Patrick Michel at France’s CNRS explains how they form this way.

The European Space Agency (ESA) spacecraft Rosetta visited 67P in 2014, end even placed its lander Philae on the surface. Rosetta spent 17 months orbiting 67P, and at its closest approach, Rosetta was only 10 km (6 mi) from 67P’s surface. Rosetta’s mission ended with its guided impact into 67P’s surface in September, 2016, but the attempt to understand the comet and its brethren didn’t end then.

An artist’s illustration of the spacecraft Rosetta and the Philae lander at comet 67P C-G. Image: By European Space Agency – Rosetta and Philae at comet, CC BY-SA 3.0-igo,

Though Rosetta’s pictures of 67P are the most detailed comet pictures we have, other spacecraft have visited other comets. And most of those other comets appear elongated or multi-lobed, too. Scientists explain these shapes with a “comet merger theory.” Two comets collide, creating the multi-lobed appearance of comets like 67P. But there’s been a problem with that theory.

In order for comets to merge and come out looking the way they do, they would have to merge very slowly, or else they would explode. They would also have to be very low-density, and be very rich in volatile elements. The “comet merger theory” also says that these types of gentle mergers between comets would have to have happened billions of years ago, in the early days of the Solar System.

The problem with this theory is, how could bodies like 67P have survived for so long? 67P is fragile, and subjected to repeated collisions in its part of the Solar System. How could it have retained its volatiles?

Geysers of dust and gas shooting off the comet’s nucleus are called jets. The volatile material they deliver outside the nucleus builds the comet’s coma. Credit: ESA/Rostta/NAVCAM

In the new paper, the research team ran a simulation that answers these questions.

The simulation showed that when two comets meet in a destructive collision, only a small portion of their material is pulverized and reduced to dust. On the sides of the comets opposite from the impact point, materials rich in volatiles withstand the collision. They’re still ejected into space, but their relative speed is low enough for them to join together in accretion. This process forms many smaller bodies, which keep clumping up until they form just one, larger body.

The most surprising part of this simulation is that this entire process may only take a few days, or even a few hours. The whole process explains how comets like 67P can keep their low density, and their abundant volatiles. And why they appear multi-lobed.

This image from the simulation shows how the ejected material from two bodies colliding re-accretes into a bilobal comet. Image: ESA/Rosetta/Navcam – CC BY-SA IGO 3.0

The simulation also answered another question: how can comets like 67P survive for so long?

The team behind the simulation thinks that the process can take place at speeds of 1 km/second. These speeds are typical in the Kuiper Belt, which is the disc of comets where 67P has its origins. In this belt, collisions between comets are a regular occurrence, which means that 67P didn’t have to form in the early days of the Solar System as previously thought. It could have formed at any time.

The team’s work also explains the surface appearance of 67P and other comets. They often have holes and stratified layers, and these features could have formed during re-accretion, or sometime after its formation.

Smooth terrain in the Imhotep region on 67P C-G, showing layering (B) and circular structures or pits (circled). Credit: ESA/Rosetta

One final point from the study concerns the composition of comets. One reason they’re a focus of such intense interest is their age. Scientists have always thought of them as ancient objects, and that studying them would allow us to look back into the primordial Solar System.

Though 67P—and other comets—may have formed much more recently than we used to believe, this process shows that there is no significant amount of heating or compaction during the collision. As a result, their original composition from the the early days of the Solar System is retained intact. No matter when 67P formed, it’s still a messenger from the formative days.

You can watch a video from the simulation here: http://www.dropbox.com/s/u7643hanvva57rp/Catastrophic%20disruptions.mp4?dl=0

Posted on by David Dickinson

Catch Sight of Humanity Star… While You Can

Humanity Star: shinny star-ball or light pollution menace. Credit Humanity Star
Humanity Star: shinny star-ball, or light pollution menace? Credit: Humanity Star.

It’s a question I’ve gotten lots, now that the calendar has flipped over from February to March. When will we get our first good look at the Humanity Star reflector satellite?

The Humanity Star satellite was a surprise payload object placed on the January 21st, 2018 inaugural orbital launch for Rocket Lab’s Electron rocket. Said launch occurred at Rocket Lab’s Launch Complex-1 on the Mahia Peninsula in New Zealand, placing Humanity Star in a 92 minute orbit inclined 83 degrees to the equator.

Launch! Electron’s inaugural flight. Credit: Rocket Lab.

Dubbed “A bright symbol and a reminder of our fragile place in the Universe,” Humanity Star is a one metre-wide reflective ball. The project is part of an effort to get humanity looking up worldwide in an effort to raise awareness about the night sky and space. Apparently, the cheap showiness of the natural night sky just isn’t enough to drag kids from their smartphone screens these days…

The Upcoming Passes

It makes sense to put a low priority payload such as a shinny orbiting ball or a Tesla roadster on an inaugural rocket launch. Anything can happen the first time ’round, and you wouldn’t want to say, bet the success of the James Webb Space Telescope on an untested launch platform.

And since placing Humanity Star in orbit was a secondary objective for Electron, the orbit is a tough one to observe. It’s just now becoming visible around middle latitudes this week over the swath of the planet inhabited by most of well, humanity.

Heavens-Above’s main page has a link dedicated to Humanity Star. Early magnitude estimates place its maximum brightness on a good overhead pass at around magnitude +1—visible to the naked eye, but hardly the “Brightest Object in the Heavens!” proclaimed on many websites.

The Friday, March 9th pass of Humanity Star up the U.S. East Coast at 7:13 PM EST. Credit: Orbitron.

And what goes up, must come back down. Very early predictions by the U.S. Joint Space Operations Command’s Space-Track website place the reentry for Humanity Star at sometime around March 25th. We’ll be watching for Humanity Star from our current base camp of operations in Norfolk, Virginia this week, clear skies willing. Follow us on Twitter (we’re @Astroguyz) for updates on sightings, magnitude etc.

There’s no word yet as to when the next Electron rocket launch from New Zealand by Rocket Lab will take place.

Is it good to put shinny junk in space? Another recent effort, the Russian Mayak reflector satellite from 2017, proved to be underwhelming. The first constellation of Iridium satellites will reenter over the next few years, marking the end of the Iridium Flare Era. One Japanese company even wants to provide customized artificial meteor showers.

It reminds me of the good old/bad old days of the 1970s, when plans were afoot to place everything in orbit, from large reflectors to abolish the night (!) to orbiting advertising. And while our astrophotos aren’t getting photo-bombed by Pepsi or McDonald’s logos (yet), we can all chase down the latest attempt to get folks to look up this weekend.

Posted on by Evan Gough

Astronomers See A Dead Star Come Back To Life Thanks To A Donor Star

The ESA INTEGRA observatory has witnessed a "zombie" neutron star being re-energized by the solar wind of its companion red giant star, and coming back to life in a burst of x-rays. Image: ESA

It’s not exactly an organ donor, but a star in the direction of the hyper-populated core of the Milky Way donating some of its mass to a dormant neighbor. The result? The dormant neighbor sprung back to life with an X-ray burst captured by the ESA‘s INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) space observatory.

“INTEGRAL caught a unique moment in the birth of a rare binary system” – Enrico Bozzo, University of Geneva.

The neighbors have likely been paired together for billions of years, which is not in itself noteworthy: stars often live in binary pairs. But the pair spotted by INTEGRAL on August 13th 2017 is very unusual. The donor star is a red giant, and the recipient is a neutron star. So far, astronomers only know of 10 of these pairs, called ‘symbiotic X-ray binaries’.

To understand what’s happening between these neighbors, we have to look at stellar evolution.

The donor star is in its red giant phase. That’s when a star in the same mass range as our star reaches the later stage of its life. As its mass is depleted, gravity can’t hold the star together in the same way it has for the early part of its life. The star expands outwards by millions of kilometers. As it does so, it sheds stellar material from its outer layers in a solar wind that travels several hundreds of km/sec.

The red giant and the neutron star may have traveled different evolutionary pathways, but proximity made them partners. Image: ESA

Its neighbor is in a different state. It’s a star that had an initial mass of about 25 to 30 times the Sun. When a star this big approaches the end of its life, it suffers a different fate. Stars this large live fast, and burn through their fuel quickly. Then, they explode as supernovae, in this case leaving a corpse behind. In the binary system captured by INTEGRAL, the corpse is a spinning neutron star with a magnetic field.

Neutron stars are dense. In fact, they’re some of the densest stellar objects we know of, packing as much mass as one-and-a-half of our Suns into an object that’s only about 10 km across.
When the red giant’s stellar wind met the neutron star, the neutron star slowed its rate of spin, and burst into life, emitting high-energy x-rays.

“INTEGRAL caught a unique moment in the birth of a rare binary system,” says Enrico Bozzo from University of Geneva and lead author of the paper that describes the discovery. “The red giant released a sufficiently dense slow wind to feed its neutron star companion, giving rise to high-energy emission from the dead stellar core for the first time.”

After INTEGRAL spotted the x-ray burst from the binary, other observations quickly followed. The ESA’s XMM Newton and NASA’s NuSTAR and Swift space telescopes got to work, along with ground-based telescopes. These observations confirmed what initial observations showed: this is a very peculiar pair of stars.

“…we believe we saw the X-rays turning on for the first time.” – Erik Kuulkers, ESA INTEGRAL Project Scientist.

The neutron star spins very slowly, taking about 2 hours to revolve, which is remarkable since other neutron stars can spin many times per second. The magnetic field of the neutron star was also much stronger than expected. But the magnetic field around a neutron star is thought to weaken over time, making this a relatively young neutron star. And a red giant is old, so this is a very odd pairing of old red giant with young neutron star.

One possible explanation is that the neutron star didn’t form from a supernova, but from a white dwarf. In that scenario, the white dwarf would’ve collapsed into a neutron star after a very long period of feeding on material from the red giant. That would explain the disparity in ages of the two stars in the system.

An artist’s illustration of ESA’s INTEGRAL space observatory. INTEGRAL was launched in 2002 to study some of the most energetic phenomena in the universe. Image: ESA.

“These objects are puzzling,” says Enrico. “It might be that either the neutron star magnetic field does not decay substantially with time after all, or the neutron star actually formed later in the history of the binary system. That would mean it collapsed from a white dwarf into a neutron star as a result of feeding off the red giant over a long time, rather than becoming a neutron star as a result of a more traditional supernova explosion of a short-lived massive star.”

The next question is how long will this process go on? Is it short-lived, or the beginning of a long-term relationship?

“We haven’t seen this object before in the past 15 years of our observations with INTEGRAL, so we believe we saw the X-rays turning on for the first time,” says Erik Kuulkers, ESA’s INTEGRAL project scientist. “We’ll continue to watch how it behaves in case it is just a long ‘burp’ of winds, but so far we haven’t seen any significant changes.”

The INTEGRAL space observatory was launched in 2002 to study some of the most energetic phenomena in the universe. It focuses on things like black holes, neutron stars, active galactic nuclei and supernovae. INTEGRAL is a European Space Agency mission in cooperation with the United States and Russia. Its projected end date is December, 2018.

Posted on by Matt Williams

Scientists Find that Earth Bacteria Could Thrive on Enceladus

Scientists recently determined that a certain strain of Earth bacteria could thrive under conditions found on Enceladus. Credit: NASA/JPL/Space Science Institute

For decades, ever since the Pioneer and Voyager missions passed through the outer Solar System, scientists have speculated that life might exist within icy bodies like Jupiter’s moon Europa. However, thanks the Cassini mission, scientists now believe that other moons in the outer Solar System – such as Saturn’s moon Enceladus – could possibly harbor life as well.

For instance, Cassini observed plume activity coming from Enceladus’ southern polar region that indicated the presence of hydrothermal activity inside. What’s more, these plumes contained organic molecules and hydrated minerals, which are potential indications of life. To see if life could thrive inside this moon, a team of scientists conducted a test where strains of Earth bacteria were subjected to conditions similar to what is found inside Enceladus.

The study which details their findings recently appeared in the journal Nature Communications under the title “Biological methane production under putative Enceladus-like conditions“. The study was led by Ruth-Sophie Taubner from the University of Vienna, and included members from the Johannes Kepler University Linz, Ecotechnology Austria, the University of Bremen, and the University of Hamburg.

Artist’s rendering of possible hydrothermal activity that may be taking place on and under the seafloor of Enceladus. Credit: NASA/JPL

For the sake of their study, the team chose to work with three strains of methanogenic archaea known as methanothermococcus okinawensis. This type of microorganism thrives in low-oxygen environments and consumes chemical products known to exist on Enceladus – such as methane (CH4), carbon dioxide (CO2 ) and molecular hydrogen (H2) – and emit methane as a metabolic byproduct. As they state:

“To investigate growth of methanogens under Enceladus-like conditions, three thermophilic and methanogenic strains, Methanothermococcus okinawensis (65 °C), Methanothermobacter marburgensis (65 °C), and Methanococcus villosus (80 °C), all able to fix carbon and gain energy through the reduction of CO2 with H2 to form CH4, were investigated regarding growth and biological CH4 production under different headspace gas compositions…”

These strains were selected because of their ability to grow in a temperature range that is characteristic of the vicinity around hydrothermal vents, in a chemically defined medium, and at low partial pressures of molecular hydrogen. This is consistent with what has been observed in Enceladus’ plumes and what is believed to exist within the moon’s interior.

These types of archaea can still be found on Earth today, lingering in deep-see fissures and around hydrothermal vents. In particular, the strain of M. okinawensis has been determined to exist in only one location around the deep-sea hydrothermal vent field at Iheya Ridge in the Okinawa Trough near Japan. Since this vent is located at a depth of 972 m (3189 ft) below sea level, this suggests that this strain has a tolerance toward high pressure.

Hydrothermal vents on Earth’s ocean floor. Credit: NOAA

For many years, scientists have suspected that Earth’s hydrothermal vents played a vital role in the emergence of life, and that similar vents could exist within the interior of moons like Europa, Ganymede, Titan, Enceladus, and other bodies in the outer Solar System. As a result, the research team believed that methanogenic archaea could also exist within these bodies.

After subjecting the strains to Enceladus-like temperature, pressure and chemical conditions in a laboratory environment, they found that one of the three strains was able to flourish and produce methane. The strain even managed to survive after the team introduced harsh chemicals that are present on Enceladus, and which are known to inhibit the growth of microbes. As they conclude in their study:

“In this study, we show that the methanogenic strain M. okinawensis is able to propagate and/or to produce CH4 under putative Enceladus-like conditions. M. okinawensis was cultivated under high-pressure (up to 50 bar) conditions in defined growth medium and gas phase, including several potential inhibitors that were detected in Enceladus’ plume.”

From this, they determined that some of the methane found in Enceladus’ plumes were likely produced by the presence of methanogenic microbes. As Simon Rittmann, a microbiologist at the University of Vienna and lead author of the study, explained in an interview with The Verge. “It’s likely this organism could be living on other planetary bodies,” he said. “And it could be really interesting to investigate in future missions.”

Artist impression of an interior cross-section of the crust of Enceladus, which shows how hydrothermal activity may be causing the plumes of water at the moon’s surface. Credits: NASA-GSFC/SVS, NASA/JPL-Caltech/Southwest Research Institute

In the coming decades, NASA and other space agencies plan to send multiple mission to the Jupiter and Saturn systems to investigate their “ocean worlds” for potential signs of life. In the case of Enceladus, this will most likely involve a lander that will set down around the southern polar region and collect samples from the surface to determine the presence of biosignatures.

Alternately, an orbiter mission may be developed that will fly through Enceladus’ plumes and collect bioreadings directly from the moon’s ejecta, thus picking up where Cassini left off. Whatever form the mission takes, the discoveries are expected to be a major breakthrough. At long last, we may finally have proof that Earth is not the only place in the Solar System where live can exist.

Be sure to check out John Michael Godier’s video titled “Encedalus and the Conditions for Life” as well:

Further Reading: The Verge, Nature