Posted on by Paul Scott Anderson

Scientists Find New Clues About the Interiors of ‘Super-Earth’ Exoplanets

Artist's conception of "Super-Earth" exoplanet Kepler-22b, which is about 2.4 times larger than Earth. Credit: NASA.

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As we learned in science class in school, the Earth has a molten interior (the outer core) deep beneath its mantle and crust. The temperatures and pressures are increasingly extreme, the farther down you go. The liquid magmas can “melt” into different types, a process referred to as pressure-induced liquid-liquid phase separation. Graphite can turn into diamond under similar extreme pressures. Now, new research is showing that a similar process could take place inside “Super-Earth” exoplanets, rocky worlds larger than Earth, where a molten magnesium silicate interior would likely be transformed into a denser state as well.

Simply put, the magnesium silicate undergoes what’s called a phase change while in the liquid state. The scientists were able to replicate the extreme temperatures and pressures that would be found inside those exoplanets by using the Janus laser at the Lawrence Livermore National Laboratory and OMEGA at the University of Rochester. A powerful laser pulse generated a shock wave as it passed through the samples. Changes in the velocity of the shock and the temperature of the sample indicated when a phase change was detected.

Interestingly, the different liquid states of the silicate magma in the experiments showed different physical properties under high pressures and temperatures, even though they were still of the same composition. Due to varying densities, the different liquid states tended to want to separate, much like oil and water.

The findings should help to better understand the interiors of terrestrial-type exoplanets, whether they are “Super-Earths” or smaller, like Earth or Mars.

Lead scientist Dylan Spaulding, at the University of California, Berkeley, states: “Phase changes between different types of melts have not been taken into account in planetary evolution models. But they could have played an important role during Earth’s formation and may indicate that extra-solar ‘Super-Earth’ planets are structured differently from Earth.”

The paper was published in the February 10, 2012 edition of the journal Physical Review Letters.

Posted on by Ray Sanders

How Well Can Astronomers Study Exoplanet Atmospheres?

Artist's impression of exoplanets around other stars. Credits: ESA/AOES Medialab

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Exoplanet discoveries are happening at a frenetic pace, and some of the latest newly discovered worlds are sometimes described as “Earth-Like” and “potentially habitable.”

The basis of this comparison is, in many cases, based on the distance between the exoplanet and its host star. Unfortunately the distance between a planet and its host star is only half the picture. The other half is determining if an exoplanet has an atmosphere, and what the contents of said atmosphere may be.

Basically, just because an exoplanet is in the “habitable zone” around its host star, it may not necessarily be habitable. If an exoplanet has a thick, crushing, Venus-Like atmosphere, it would most likely be too hot for surface water. The opposite holds true as well, as it could be entirely possible for an exoplanet to have a thin, wispy Mars-like atmosphere where any water would be locked up as ice.

At this point, how well can astronomers study the atmosphere around an exoplanet?

The spectrum from a giant exoplanet, orbiting around the bright, young, star HR 8799. Image Credit: ESO/M. Janson
Currently, there are only a handful of methods researchers can use to make estimates of exoplanet atmospheres. Interestingly enough, one method makes use of the light coming from the host star. The basic principle is that the light from a star can be analyzed both before and after an exoplanet crosses in front of the star. By comparing the spectrum from the host star, and the spectrum of an exoplanet, the tell-tale signs of atmospheric contents can be detected.

Methods to detect the atmospheric composition of such distant worlds are fairly new, as shown by work done with the Spitzer Space Telescope and ESO’s Very Large Telescope

Recently, astronomers from The Sternberg Astronomical Institute at Moscow State University used data from the Hubble Space Telescope in an attempt to better detect atmospheres around exoplanets. Abubekerov and team created mathematical models to analyze light curves from distant stars. In the case of Abubekerov’s research, the selected star was HD 189733 – a K-class star a bit cooler and smaller than our Sun.

About 60 light-years from Earth, HD 189733 also happens to have a binary companion orbiting it at a radius of about 200 A.U. So far, one exoplanet is known to orbit HD 189733. Discovered in 2005, HD 189733 b is a roughly Jupiter-size exoplanet which orbits its host star in just over two days. While not mentioned directly in Abubekerov’s paper, other studies have detected methane, carbon monoxide, water vapor and sodium in HD 189733 b’s atmosphere.

Light curve from HD 189733 in 5500 - 6000 angstrom range.
By applying their models to the light curves from HD 189733, Abubekerov’s team was able to better understand how light at different wavelengths behaves when an exoplanet crosses in front of its host star.

According to Abubekerov and team, the end result of their research was unsuccessful. The team suspects dark spot activity on HD 189733 was a contributing factor to their models not agreeing with actual observations.

The team stressed that additional observational data from HD 189733 when spot activity is negligible would be required to further refine their work. Despite their models not being successful, the team is confident that exoplanet radius increases with decreasing wavelength, which may imply the presence of an atmosphere.

Research such as Abubekerov’s will help astronomers build better models and pave the way for “sniffing” exoplanet atmospheres. Newer technology such as the James Webb Space Telescope and the European Extremely Large Telescope will also provide better data. In the not-too-distant future, astronomers and astrobiologists should be able to examine the atmospheres of exoplanets in the habitable zone.

If you’d like to read the full research paper, you can access a pre-print version at: http://arxiv.org/pdf/1201.4043v1.pdf

Source(s): Analysis of Light Curves of Eclipsing Systems with Exoplanets:
HD 189733. M. K. Abubekerov, N. Yu. Gostev, and A. M. Cherepashchuk , Extrasolar Planets Encyclopaedia

Posted on by Mike Simonsen

Goldilocks Moons

The Goldilocks Zones around various type stars. Credit: NASA/JPL-Caltech

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The search for extraterrestrial life outside our Solar System is currently focused on extrasolar planets within the ‘habitable zones’ of exoplanetary systems around stars similar to the Sun. Finding Earth-like planets around other stars is the primary goal of NASA’s Kepler Mission.

The habitable zone (HZ) around a star is defined as the range of distances over which liquid water could exist on the surface of a terrestrial planet, given a dense enough atmosphere. Terrestrial planets are generally defined as rocky and similar to Earth in size and mass. A visualization of the habitable zones around stars of different diameters and brightness and temperature is shown here. The red region is too hot, the blue region is too cold, but the green region is just right for liquid water. Because it can be described this way, the HZ is also referred to as the “Goldilocks Zone”.

Normally, we think of planets around other stars as being similar to our solar system, where a retinue of planets orbits a single star. Although theoretically possible, scientists debated whether or not planets would ever be found around pairs of stars or multiple star systems. Then, in September, 2011, researchers at NASA’s Kepler mission announced the discovery of Kepler-16b, a cold, gaseous, Saturn-sized planet that orbits a pair of stars, like Star Wars’ fictional Tatooine.

This week I had the chance to interview one of the young guns studying exoplanets, Billy Quarles. Monday, Billy and his co-authors, professor Zdzislaw Musielak and associate professor Manfred Cuntz, presented their findings on the possibility of Earth-like planets inside the habitable zones of Kepler 16 and other circumbinary star systems, at the AAS meeting in Austin, Texas.

The Goldilocks Zones around various type stars. Credit: NASA/JPL-Caltech

“To define the habitable zone we calculate the amount of flux that is incident on an object at a given distance,” Billy explained. “We also took into account that different planets with different atmospheres will retain heat differently. A planet with a really weak greenhouse effect can be closer in to the stars. For a planet with a much stronger greenhouse effect, the habitable zone will be further out.”

“In our particular study, we have a planet orbiting two stars. One of the stars is much brighter than the other. So much brighter, that we ignored the flux coming from the smaller fainter companion star altogether. So our definition of the habitable zone in this case is a conservative estimate.”

Quarles and his colleagues performed extensive numerical studies on the long-term stability of planetary orbits within the Kepler 16 HZ. “The stability of the planetary orbit depends on the distance from the binary stars,” said Quarles. “The further out the more stable they tend to be, because there is less perturbation from the secondary star.”

For the Kepler 16 system, planetary orbits around the primary star are only stable out to 0.0675 AU (astronomical units). “That is well inside the inner limit of habitability, where the runaway greenhouse effect takes over,” Billy explained. This all but rules out the possibility of habitable planets in close orbit around the primary star of the pair. What they found was that orbits in the Goldilocks Zone farther out, around the pair of Kepler 16’s low-mass stars, are stable on time scales of a million years or more, providing the possibility that life could evolve on a planet within that HZ.

Kepler 16's orbit from Quarles et al

Kepler 16b’s roughly circular orbit, about 65 million miles from the stars, is on the outer edge of this habitable zone. Being a gas giant, 16b is not a habitable terrestrial planet. However, an Earth-like moon, a Goldilocks Moon, in orbit around this planet could sustain life if it were massive enough to retain an Earth-like atmosphere. “We determined that a habitable exomoon is possible in orbit around Kepler-16b,” Quarles said.

I asked Quarles how stellar evolution impacts these Goldilocks Zones. He told me, “There are a number of things to consider over the lifetime of a system. One of them is how the star evolves over time. In most cases the habitable zone starts out close and then slowly drifts out.”

During a star’s main sequence lifetime, nuclear burning of hydrogen builds up helium in its core, causing an increase in pressure and temperature. This occurs more rapidly in stars that are more massive and lower in metallicity. These changes affect the outer regions of the star, which results in a steady increase in luminosity and effective temperature. The star becomes more luminous, causing the HZ to move outwards. This movement could result in a planet within the HZ at the beginning of a star’s main sequence lifetime, to become too hot, and eventually, uninhabitable. Similarly, an inhospitable planet originally outside the HZ, may thaw out and enable life to commence.

“For our study, we ignored the stellar evolution part,” said lead author, Quarles. “We ran our models for a million years to see where the habitable zone was for that part of the star’s life cycle.”

Being at the right distance from its star is only one of the necessary conditions required for a planet to be habitable. Habitable conditions on a planet require various geophysical and geochemical conditions. Many factors can prevent, or impede, habitability. For example, the planet may lack water, gravity may be too weak to retain a dense atmosphere, the rate of large impacts may be too high, or the minimum ingredients necessary for life (still up for debate) may not be there.

One thing is clear. Even with all the requirements for life as we know it, there appear to be plenty of planets around other stars, and very likely, Goldilocks Moons around planets, orbiting within the habitable zones of stars in our galaxy, that detecting the signature of life in the atmosphere of a planet or moon around another Sun seems like only a matter of time now.

Posted on by Ken Kremer

NASA’s Unprecedented Science Twins are GO to Orbit our Moon on New Year’s Eve

GRAIL probes uses precision formation-flying technique to map Lunar Gravity. The twin GRAIL spacecraft will map the moon's gravity field, as depicted in this artist's rendering. Radio signals traveling between the two spacecraft provide scientists the exact measurements required as well as flow of information not interrupted when the spacecraft are at the lunar farside, not seen from Earth. The result should be the most accurate gravity map of the moon ever made. The mission also will answer longstanding questions about Earth's moon, including the size of a possible inner core, and it should provide scientists with a better understanding of how Earth and other rocky planets in the solar system formed. GRAIL is a part of NASA's Discovery Program. Credit: NASA/JPL-Caltech

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In less than three days, NASA will deliver a double barreled New Year’s package to our Moon when an unprecedented pair of science satellites fire up their critical braking thrusters for insertion into lunar orbit on New Year’s Eve and New Year’s Day.

NASA’s dynamic duo of GRAIL probes are “GO” for Lunar Orbit Insertion said the mission team at a briefing for reporters today, Dec. 28. GRAIL’s goal is to exquisitely map the moons interior from the gritty outer crust to the depths of the mysterious core with unparalled precision.

“GRAIL is a Journey to the Center of the Moon”, said Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology (MIT) in Cambridge at the press briefing.

This newfound knowledge will fundamentally alter our understanding of how the moon and other rocky bodies in our solar system – including Earth – formed and evolved over 4.5 Billion years time.

After a three month voyage of more than 2.5 million miles (4 million kilometers) since launching from Florida on Sept. 10, 2011, NASA’s twin GRAIL spacecraft, dubbed Grail-A and GRAIL-B, are now on final approach and are rapidly closing in on the Moon following a trajectory that will hurl them low over the south pole and into an initially near polar elliptical lunar orbit lasting 11.5 hours.

GRAIL's trajectory to moon since Sept. 10, 2011 blastoff
Credit: NASA/JPL-Caltech

As of today, Dec. 28, GRAIL-A is 65,860 miles (106,000 kilometers) from the moon and closing at a speed of 745 mph (1,200 kph). GRAIL-B is 79,540 miles (128,000 kilometers) from the moon and closing at a speed of 763 mph (1,228 kph).

The lunar bound probes are formally named Gravity Recovery And Interior Laboratory (GRAIL) and each one is the size of a washing machine.

The long-duration trajectory was actually beneficial to the mission controllers and the science team because it permitted more time to assess the spacecraft’s health and check out the probes single science instrument – the Ultra Stable Oscillator – and allow it to equilibrate to a stable operating temperature long before it starts making the crucial science measurements.

NASA’s twin GRAIL A & B Moon mapping probes
The GRAIL satellites are now streaking to the Moon and their arrival for orbit insertion is just days away and hours apart on New Year’s Eve and New Year’s Day 2012. This picture shows how they looked, mounted side by side, during launch preparations inside the clean room at Astrotech Space Operations facility in Florida prior to blasting off for the Moon on Sept. 10, 2011 from Cape Canaveral, Florida. Credit: Ken Kremer

The duo will arrive 25 hours apart and be placed into orbit starting at 1:21 p.m. PST (4:21 p.m. EST) for GRAIL-A on Dec. 31, and 2:05 p.m. PST (5:05 p.m. EST) on Jan. 1 for GRAIL-B, said David Lehman, project manager for GRAIL at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

“The GRAIL A burn will last 40 minutes and the GRAIL-B burn will last 38 minutes. One hour after the burn we will know the results and make an announcement,” Lehman explained.

The thrusters must fire on time and for the full duration for the probes to achieve orbit. The braking maneuver is preprogrammed and done completely automatically.

Over the next few weeks, the altitude of the spacecraft will be gradually lowered to 34 miles (55 kilometers) into a near-polar, near-circular orbit with an orbital period of two hours. The science phase will then begin in March 2012.

“So far there have been over 100 missions to the Moon and hundreds of pounds of rock have been returned. But there is still a lot we don’t know about the Moon even after the Apollo lunar landings,” explained Zuber.

“We don’t know why the near side of the Moon is different from the far side. In fact we know more about Mars than the Moon.”

GRAIL’s science collection phase will last 82 days. The two spacecraft will transmit radio signals that will precisely measure the distance between them to within a few microns, less than the width of a human hair.

Artist concept of twin GRAIL spacecraft flying in tandem orbits around the moon to measure its gravity field in unprecedented detail. Credit: NASA/JPL

As they orbit in tandem, the moons gravity will change – increasing and decreasing due to the influence of both visible surface features such as mountains and craters and unknown concentrations of masses hidden beneath the lunar surface. This will cause the relative velocity and the distance between the probes to change.

The resulting data will be translated into a high-resolution map of the Moon’s gravitational field and also enable determinations of the moon’s inner composition.

The GRAIL mission may be extended for another 6 months if the solar powered probes survive a power draining and potentially deadly lunar eclipse due in June 2012.

Engineers would significantly lower the orbit to an altitude of barely 15 to 20 miles above the surface to gain even further insights into the lunar interior.

The twin probes are also equipped with 4 cameras each – named MoonKAM – that will be used by middle school students to photograph student selected targets.

The MoonKAM project is led Dr. Sally Ride, America’s first woman astronaut as a way to motivate kids to study math and science.

JPL manages the GRAIL mission for NASA.

Stay tuned for Universe Today updates amidst the News Year’s festivities.

Blastoff of twin GRAIL A and B lunar gravity mapping spacecraft on a Delta II Heavy rocket on Sept. 10 from Pad 17B Cape Canaveral Air Force Station in Florida at 9:08 a.m. EDT. Credit: Ken Kremer

Read continuing features about GRAIL by Ken Kremer here:
Student Alert: GRAIL Naming Contest – Essay Deadline November 11
GRAIL Lunar Blastoff Gallery
GRAIL Twins Awesome Launch Videos – A Journey to the Center of the Moon
NASA launches Twin Lunar Probes to Unravel Moons Core
GRAIL Unveiled for Lunar Science Trek — Launch Reset to Sept. 10
Last Delta II Rocket to Launch Extraordinary Journey to the Center of the Moon on Sept. 8
NASAs Lunar Mapping Duo Encapsulated and Ready for Sept. 8 Liftoff
GRAIL Lunar Twins Mated to Delta Rocket at Launch Pad
GRAIL Twins ready for NASA Science Expedition to the Moon: Photo Gallery

Posted on by Ray Sanders

Dr. Alan Stern Answers Your Questions!

Dr. Alan Stern preparing for a high-altitude test flight in A two-seater, NASA WB-57 aircraft. Photo Credit: SOuthwest Research Institute.

[/caption]Some of you may know, we recently launched a new “Ask” feature here at Universe Today. Our inaugural launch features Dr. Alan Stern, Principal Investigator for the New Horizons mission to Pluto and the Kuiper Belt. We collected your questions in our initial post and passed them along to Dr. Stern who graciously took the time to answer them.

Here are the questions picked by you, the readers, and Dr. Stern’s responses. We’d like to thank our readers for making this kick-off a success, as well as Dr. Stern for his participation.


1.) Many sci-fi authors have dreamed of putting some sort of telescope on the surface of Pluto to take advantage of the relative darkness and extreme cold encountered on this distant dwarf planet. How feasible would it be, judging from what we’re learning from the New Horizons expedition, to actually land a spacecraft, or a telescope, on Pluto’s surface? If such a telescope where deployed, how much more effective, if at all, could it be than an instrument like the JWST?

Alan Stern:“Space astronomy has revolutionized the way we look at the universe and is fundamental to modern astrophysics.” There are benefits to getting telescopes out of the atmosphere, and even benefits to getting out of Earth orbit, as in the case of Kepler and someday maybe JWST.

With regard to taking advantage of Pluto’s cold temperature – we’ve gotten really good at cooling down space telescopes. “There would be a benefit to placing a radio telescope on the far side of the Moon, but there’s no real practical reasons to place a telescope on Pluto—particularly given the cost of getting there, other than it being cool.”

2.) Kuiper objects differentiate strongly in color suggesting compositional or perhaps formation differences. Interestingly the color distribution correlates with the two different cold and hot Kuiper populations. Assuming the spectral analysis capability of New Horizon works for identifying the follow up Kuiper objects beyond Pluto-Charon, and given the putative possibility of choosing between several such targets, what type of target would the mission aim for? Would it try to cover as much diversity of objects as possible or is there a certain class of objects that could be important to concentrate on?

A.S: “We have to find Kuiper belt objects within our spacecraft’s fuel supply.” Stern elaborated, stating, “Predictions from our computer models tell us to expect to be able to have perhaps six possible candidates, to choose from, but so far we’ve just begun to search for these and though we’re finding KBOs, none we’ve found are yet are within the fuel supply.”

Stern also added, “Keep in mind our search for candidates isn’t easy – these are 27th magnitude objects which are roughly 50,000 times fainter than Pluto. What we’ll use to select between candidates once we have them are color, orbits, moons, rotational speeds – basically what combination of properties give us the most science for our fuel budget. The longer we wait after the Pluto flyby in July 2015 to make a decision, the more fuel will be consumed, so the “sweet spot” would be to have preliminary candidates in early 2015.”
(UT Note: New Horizons will perform its Pluto flyby in mid-2015 ).

3.) Given the limited funds available, Which do you recommend (Europa or Enceladus) as a suitable target for a mission in the 2025 time-frame in terms of value for money, scientific return, and practicality, and what kind of mission do you propose (lander vs. orbiter) ?

A.S: “Every scientist has their own judgment of what would make a good outer system flagship mission, or the best world to perform a series of missions that would equal a flagship mission.” Dr. Stern’s opinion is to explore Titan first, with Enceladus as a secondary target of that mission and Europa last, stating “Titan is the belle of the ball”, citing Titan’s active liquid cycle and thick atmosphere. Stern also added that he believes a mission to Titan would provide the most science per budget dollar.

4.) Four of the craft escaping the Solar System – Pioneers 10 & 11 and Voyagers 1 & 2 – have on board some sort of “message” to any possible extraterrestrials in the unlikely event they find it. Why was not some sort of message like that included on New Horizons, which may be the last (in our lifetimes) craft to also escape the Solar System?

A.S “There are several mementos onboard New Horizons, but no Voyager-like message.” Dr. Stern discussed a promise he made to his team that New Horizons would not be canceled and that he wanted his team focused on the science of the mission. Stern also pointed out that the process of deciding what to place on the Voyager plaques became mired in political correctness, (should the humans have been clothed? What cultures and races should be represented, etc.)

By separating the “icing from the cake”. Stern and his team have been able to concentrate on their main objective—to execute the New Horizons mission for about twenty cents on the dollar, as compared to the Voyager missions. Stern concluded with, “I’m proud that we got this done and that New Horizons is operating perfectly now way out there between Uranus and Neptune and flying almost a million kilometers per day toward the Pluto system.”

5.) Are any present or foreseeable technologies being considered for exploring the depths of our four “gas giant” planets?

A.S “There are no serious proposals to put a probe into one of the giant planets now, or even any call for such in the recent decadal survey for planetary missions. Keep in mind, though, that the Juno mission (now en route to Jupiter ) will use powerful remote sensing techniques to probe Jupiter from orbit around it to greater depths than the Galileo probe (which actually entered Jupiter’s atmosphere).”

6.) Why was it considered “urgent” to get to Pluto before the atmosphere refroze?

A.S “We have three “Group 1″ objectives for New Horizons. Map the surface, map the composition, and assay the atmosphere.” Stern referred to the objectives as a “three legged stool” in that no one objective could be omitted and still justify the mission, adding “so we need to accomplish that.. we need to get there before the atmosphere collapses”. Stern also referred to Pluto’s atmosphere as “very different from any other planet yet studied”, hence its inclusion as one of the three “Group 1” objectives.

7.) The Dawn mission to Vesta has shown us a body that was much less round than expected. Do you think it is possible that New Horizons will surprise us about Pluto, to the same degree? Please compare the expectations of the New Horizons fly by, to the early images of Vesta from Dawn.

A.S “With New Horizons being the first mission to Pluto, we will be surprised—after all, we’re always surprised on first reconnaissance flybys”. Stern added, “With Mariner 10, we discovered Mercury was all core, with Voyager we discovered volcanos and geysers across the outer solar system, and of course we were surprised when craters and river valleys were discovered by early Mars probes.”

Regarding Pluto, Stern stated “Pluto is the first discovered and soon to be reconnoitered of the most plentiful class of planets, while I’m not big on making predictions, I will say that what we will find will certainly be, well, wonderful.”

9.) Can new horizons now take more detailed photos of Pluto than HST? If not, when does it get close enough?

A.S “Great question! We actually thought about that a lot when designing New Horizons. One of our instruments, LORRI (Long-Range Reconnaissance Imager – http://pluto.jhuapl.edu/spacecraft/sciencePay.html) will provide us with views better than HST around April of 2015, and we expect to have about twenty weeks (10 weeks before, 10 weeks after the Pluto flyby) when we “own” the Pluto system — and I can guarantee the best images we hope to make should be as good as Landsat images of Earth!”

That wraps up our interview with Dr. Alan Stern. Once again, we at Universe Today would like to thank Dr. Stern for his gracious participation. If you’d like to learn more about the New Horizons mission to Pluto and The Kuiper Belt, visit: http://pluto.jhuapl.edu/index.php

Next month, we’ll be having an “Ask an Astronaut” feature with Mike Fossum, Commander of Expedition 29 on the International Space Station. Stay tuned!

Posted on by Paul Scott Anderson

Is Jupiter’s Core Liquifying?

Credit: NASA/ESA/E. Karkoschka (U. Arizona)

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Jupiter, the largest and most massive planet in our solar system, may be its own worst enemy. It turns out that its central core may in fact be self-destructing, gradually liquifying and dissolving over time. This implies it was previously larger than it is now, and may dissolve altogether at some point in the future. Will Jupiter eventually destroy itself completely? No, probably not, but it may lose its heart…

The core is composed of iron, rock and ice and weighs about ten times as much as Earth. That’s still small though, compared to the overall mass of Jupiter itself, which weighs as much as 318 Earths! The core is buried deep within the thick atmosphere of hydrogen and helium. Conditions there are brutal, with a temperature of about 16,000 kelvin – hotter than the surface of the Sun – and a pressure about 40 million times greater than the atmospheric pressure on Earth. The core is surrounded by a fluid of metallic hydrogen which results from the intense pressure deep down in the atmosphere. The bulk of Jupiter though is the atmosphere itself, hence why Jupiter (and Saturn, Uranus and Neptune) are called gas giants.

One of the primary ingredients in the rock of the core is magnesium oxide (MgO). Planetary scientists wanted to see what would happen when it is subjected to the conditions found at the core; they found that it had a high solubility and started to dissolve. So if it is in a state of dissolution, then it was probably larger in the past than it is now and scientists would like to understand the process. According to David Stevenson of the California Institute of Technology, “If we can do that, then we can make a very useful statement about what Jupiter was like at genesis. Did it have a substantial core at that time? If so, was it 10 Earth masses, 15, 5?”

The findings also mean that some exoplanets which are even larger and more massive than Jupiter, and thus likely even hotter at their cores, may no longer have any cores left at all. They would be indeed be gas giants in the most literal sense.

The conditions inside Jupiter’s core can’t be duplicated in labs yet, but the spacecraft Juno should provide much more data when it arrives at and starts orbiting Jupiter in 2016.

Posted on by Ken Kremer

Dawn swoops to lowest orbit around Vesta – Unveiling Spectacular Alien World

Dawn Orbiting Vesta. This artist's concept shows NASA's Dawn spacecraft orbiting the giant asteroid Vesta. The depiction of Vesta is based on images obtained by Dawn's framing cameras. Dawn is an international collaboration of the US, Germany and Italy. Credit: NASA/JPL-Caltech

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NASA’s Dawn Asteroid Orbiter successfully spiraled down today to the closest orbit the probe will ever achieve around the giant asteroid Vesta, and has now begun critical science observations that will ultimately yield the mission’s highest resolution measurements of this spectacular body.

“What can be more exciting than to explore an alien world that until recently was virtually unknown!” Dr. Marc Rayman gushed in an exclusive interview with Universe Today. Rayman is Dawn’s Chief Engineer from NASA’s Jet Propulsion Lab (JPL) in Pasadena, Calif., and a protégé of Star Trek’s Mr. Scott.

Before Dawn, Vesta was little more than a fuzzy blob in the world’s most powerful telescopes. Vesta is the second most massive object in the main Asteroid Belt between Mars and Jupiter.

Dawn is now circling about Vesta at the lowest planned mapping orbit, dubbed LAMO for Low Altitude Mapping Orbit. The spacecraft is orbiting at an average altitude of barely 130 miles (210 kilometers) above the heavily bombarded and mysterious world that stems from the earliest eons of our solar system some 4.5 Billion years ago. Each orbit takes about 4.3 hours.

“It is both gratifying and exciting that Dawn has been performing so well,” Rayman told me.

Dawn Orbiting Over Vesta - A Hi Res Taste of What's Ahead!
This image of the giant asteroid Vesta was obtained by Dawn in the evening Nov. 27 PST (early morning Nov. 28, UTC), as it was spiraling down from its high altitude mapping orbit to low altitude mapping orbit. Low altitude mapping orbit is the closest orbit Dawn will be making, at an average of 130 miles (210 kilometers) above the giant asteroid's surface. The framing camera obtained this image of an area in the northern mid-latitudes of Vesta from an altitude of about 140 miles (230 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn arrived in orbit at Vesta in July 2011 after a nearly 4 year interplanetary cruise since blasting off atop a Delta II rocket from Cape Canaveral, Florida in September 2007. The probe then spent the first few weeks at an initial science survey altitude of about 1,700 miles (2,700 kilometers).

Gradually the spaceship spiraled down closer to Vesta using her ion propulsion thrusters.

See Vesta science orbit diagram, below, provided courtesy of Dr. Marc Rayman.

Along the way, the international science and engineering team commanded Dawn to make an intermediate stop this past Fall 2011 at the High Altitude Mapping orbit altitude (420 miles, or 680 kilometers).

“It is so cool now to have reached this low orbit [LAMO]. We already have a spectacular collection of images and other fascinating data on Vesta, and now we are going to gain even more,” Rayman told me.

“We have a great deal of work ahead to acquire our planned data here, and I’m looking forward to every bit!

Dawn will spend a minimum of 10 weeks acquiring data at the LAMO mapping orbit using all three onboard science instruments, provided by the US, Germany and Italy.

While the framing cameras (FC) from Germany and the Visible and Infrared Mapping spectrometer (VIR) from Italy will continue to gather mountains of data at their best resolution yet, the primary science focus of the LAMO orbit will be to collect data from the gamma ray and neutron detector (GRaND) and the gravity experiment.

GRaND will measure the elemental abundances on the surface of Vesta by studying the energy and neutron by-products that emanate from it as a result of the continuous bombardment of cosmic rays. The best data are obtained at the lowest altitude.

Dawn spacecraft - Science orbits at Vesta
Credit: NASA/JPL-Caltech/Marc Rayman

By examining all the data in context, scientists hope to obtain a better understanding of the formation and evolution of the early solar system.

Vesta is a proto-planet, largely unchanged since its formation, and whose evolution into a larger planet was stopped cold by the massive gravitational influence of the planet Jupiter.

“Dawn’s visit to Vesta has been eye-opening so far, showing us troughs and peaks that telescopes only hinted at,” said Christopher Russell, Dawn’s principal investigator, based at UCLA. “It whets the appetite for a day when human explorers can see the wonders of asteroids for themselves.”

After investigating Vesta for about a year, the engineers will ignite Dawn’s ion propulsion thrusters and blast away to Ceres, the largest asteroid which may harbor water ice and is another potential outpost for extraterrestrial life

Dawn will be the first spaceship to orbit two worlds and is also the first mission to study the asteroid belt in detail.

Asteroid Vesta from Dawn - Exquisite Clarity from a formerly Fuzzy Blob
NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. It was taken from a distance of about 3,200 miles (5,200 kilometers). Before Dawn, Vesta was just a fuzzy blob in the most powerful telescopes. Dawn entered orbit around Vesta on July 15, and will spend a year orbiting the body before firing up the ion propulsion system to break orbit and speed to Ceres, the largest Asteroid. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
South Polar Region of Vesta - Enhanced View
An ancient cosmic collision blasted away much of the south pole of Vesta, leaving behind an enoumous mountain about 3 times the height of Mt. Everest. NASA's Dawn spacecraft obtained this image centered on the south pole of Vesta with its framing camera on July 18, 2011 as it passed the terminator. The image has been enhanced to bring out more surface details. It was taken from a distance of about 6,500 miles (10,500 kilometers) away from the protoplanet Vesta. The smallest detail visible is about 1.2 miles (2.0 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Enhanced and annotated by Ken Kremer

Read continuing features about Dawn by Ken Kremer starting here:

Rainbow of Colors Reveal Asteroid Vesta as More Like a Planet
Vrooming over Vivid Vestan Vistas in Vibrant 3 D – Video
NASA Planetary Science Trio Honored as ‘Best of What’s New’ in 2011- Curiosity/Dawn/MESSENGER
Dawn Discovers Surprise 2nd Giant South Pole Impact Basin at Strikingly Dichotomous Vesta
Amazing New View of the Mt. Everest of Vesta
Dramatic 3 D Imagery Showcases Vesta’s Pockmarked, Mountainous and Groovy Terrain
Rheasilvia – Super Mysterious South Pole Basin at Vesta
Space Spectacular — Rotation Movies of Vesta
3 D Alien Snowman Graces Vesta
NASA Unveils Thrilling First Full Frame Images of Vesta from Dawn
Dawn Spirals Down Closer to Vesta’s South Pole Impact Basin

Posted on by Tammy Plotner

Carbon “Super Earths” – Diamond Planets

Iron, carbon, and oxygen subjected to intense temperatures and pressures form a pocket of iron oxide (bottom, center) and a darker pocket of diamond (bottom, right). Electron micrograph courtesy of Ohio State University

[/caption]During a laboratory experiment at Ohio State University, researchers were simulating the pressures and conditions necessary to form diamonds in the Earth’s mantle when they came across a surprise… A carbon “Super Earth” could exist. While endeavoring to understand how carbon might behave in other solar systems, they wondered if planets high in this element could be pressurized to the point of producing this valuable gemstone. Their findings point to the possibility that the Milky Way could indeed be home to stars where planets might consist of up to 50% diamond.

The research team is headed by Wendy Panero, associate professor in the School of Earth Sciences at Ohio State, and doctoral student Cayman Unterborn. As part of their investigation they incorporated their findings from earlier experiments into a computer modeling simulation. This was then used to create scenarios where planets existed with a higher carbon content than Earth..

The result: “It’s possible for planets that are as big as fifteen times the mass of the Earth to be half made of diamond,” Unterborn said. He presented the study Tuesday at the American Geophysical Union meeting in San Francisco.

“Our results are striking, in that they suggest carbon-rich planets can form with a core and a mantle, just as Earth did,” Panero added. “However, the cores would likely be very carbon-rich – much like steel – and the mantle would also be dominated by carbon, much in the form of diamond.”

At the center of our planet is an assumed molten iron core, overlaid with a mantle of silica-based minerals. This basic building block of Earth is what condensed from the materials in our solar cloud. In an alternate situation, a planet could form in a carbon-rich environment, thereby having a different planet structure – and a different potential for life. (Fortunately for us, our molten interior provides geothermal energy!) On a diamond planet, the heat would dissipate quickly – leading to a frozen core. On this basis, a diamond planet would have no geothermal resources, lack plate tectonics and wouldn’t be able to support either an atmosphere or a magnetic field.

“We think a diamond planet must be a very cold, dark place,” Panero said.

How did they come up with their findings? Panero and former graduate student Jason Kabbes took a miniature sample of iron, carbon, and oxygen and subjected it to pressures of 65 gigapascals and temperatures of 2,400 Kelvin (close to 9.5 million pounds per square inch and 3,800 degrees Fahrenheit – conditions similar to the Earth’s deep interior). As they observed the experiment microscopically, they saw oxygen bonding with iron to create rust… but what was left turned to pure carbon and eventually formed diamond. This led them to wonder about planetary formation implications.

“To date, more than five hundred planets have been discovered outside of our solar system, yet we know very little about their internal compositions,” said Unterborn, who is an astronomer by training.

“We’re looking at how volatile elements like hydrogen and carbon interact inside the Earth, because when they bond with oxygen, you get atmospheres, you get oceans – you get life,” Panero said. “The ultimate goal is to compile a suite of conditions that are necessary for an ocean to form on a planet.”

But don’t confuse their findings with recent, unrelated studies which involves the remnants of an expired star from a binary system. The OSU team’s finding simply suggest this type of planet could form in our galaxy, but how many or where they might be is still very open to interpretation. It’s a question that’s being investigated by Unterborn and Ohio State astronomer Jennifer Johnson.

Because diamonds are forever…

Original Story Source: Ohio State Research News.

Posted on by Tammy Plotner

Asteroid Lutetia… A Piece Of Earth?

This image of the unusual asteroid Lutetia was taken by ESA’s Rosetta probe during its closest approach in July 2010. Lutetia, which is about 100 kilometres across, seems to be a leftover fragment of the same original material that formed the Earth, Venus and Mercury. It is now part of the main asteroid belt, between the orbits of Mars and Jupiter, but its composition suggests that it was originally much closer to the Sun. Credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

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According to data received from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes, strange asteroid Lutetia could be a real piece of the rock… the original material that formed the Earth, Venus and Mercury! By examining precious meteors which may have formed at the time of the inner Solar System, scientists have found matching properties which indicate a relationship. Independent Lutetia must have just moved its way out to join in the main asteroid belt…

A team of astronomers from French and North American universities have been hard at work studying asteroid Lutetia spectroscopically. Data sets from the OSIRIS camera on ESA’s Rosetta spacecraft, ESO’s New Technology Telescope (NTT) at the La Silla Observatory in Chile, and NASA’s Infrared Telescope Facility in Hawaii and Spitzer Space Telescope have been combined to give us a multi-wavelength look at this very different space rock. What they found was a very specific type of meteorite called an enstatite chondrite displayed similar content which matched Lutetia… and what is theorized as the material which dates back to the early Solar System. Chances are very good that enstatite chondrites are the same “stuff” which formed the rocky planets – Earth, Mars and Venus.

“But how did Lutetia escape from the inner Solar System and reach the main asteroid belt?” asks Pierre Vernazza (ESO), the lead author of the paper.

It’s a very good question considering that an estimated less than 2% of the material which formed in the same region of Earth migrated to the main asteroid belt. Within a few million years of formation, this type of “debris” had either been incorporated into the gelling planets or else larger pieces had escaped to a safer, more distant orbit from the Sun. At about 100 kilometers across, Lutetia may have been gravitationally influenced by a close pass to the rocky planets and then further affected by a young Jupiter.

“We think that such an ejection must have happened to Lutetia. It ended up as an interloper in the main asteroid belt and it has been preserved there for four billion years,” continues Pierre Vernazza.

Asteroid Lutetia is a “real looker” and has long been a source of speculation due to its unusual color and surface properties. Only 1% of the asteroids located in the main belt share its rare characteristics.

“Lutetia seems to be the largest, and one of the very few, remnants of such material in the main asteroid belt. For this reason, asteroids like Lutetia represent ideal targets for future sample return missions. We could then study in detail the origin of the rocky planets, including our Earth,” concludes Pierre Vernazza.

Original Story Source: ESO News Release.

Posted on by Ray Sanders

Was a Fifth Giant Planet Expelled from Our Solar System?

Artist’s impression of a fifth giant planet being ejected from the solar system. Image credit: Southwest Research Institute

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Earth’s place in the “Goldilocks” zone of our solar system may be the result of the expulsion of a fifth giant planet from our solar system during its first 600 million years, according to a recent journal publication.

“We have all sorts of clues about the early evolution of the solar system,” said author Dr. David Nesvorny of the Southwest Research Institute. “They come from the analysis of the trans-Neptunian population of small bodies known as the Kuiper Belt, and from the lunar cratering record.”

Nesvorny and his team used the clues they had to build computer simulations of the early solar system and test their theories. What resulted was an early solar system model that has quite a different configuration than today, and a jumbling of planets that may have given Earth the “preferred” spot for life to evolve.


Researchers interpret the clues as evidence that the orbits of Jupiter, Saturn, Uranus and Neptune were affected by a dynamical instability when our solar system was only about half a billion years old. This instability is believed to have helped increase the distance between the giant planets, along with scattering smaller bodies. The scattering of small bodies pushed objects both inward, and outward with some objects ending up in the Kuiper Belt and others impacting the terrestrial planets and the Moon. Jupiter is believed to have scattered objects outward as it moved in towards the sun.

One problem with this interpretation is that slow changes to Jupiter’s orbit would most likely add too much momentum to the orbits of the terrestrial planets. The additional momentum would have possibly caused a collision of Earth with Venus or Mars.

“Colleagues suggested a clever way around this problem,” said Nesvorny. “They proposed that Jupiter’s orbit quickly changed when Jupiter scattered off of Uranus or Neptune during the dynamical instability in the outer solar system.”

Basically if Jupiter’s early migration “jumps,” the orbital coupling between the terrestrial planets and Jupiter is weaker, and less harmful to the inner solar system.

Animation showing the evolution of the planetary system from 20 million years before the ejection to 30 million years after. Five initial planets are shown by red circles, small bodies are in green.
After the fifth planet is ejected, the remaining four planets stabilize after a while, and looks like the outer solar system in the end, with giant planets at 5, 10, 20 and 30 astronomical units.
Click image to view animation. Image Credit: Southwest Research Institute

Nesvorny and his team performed thousands of computer simulations that attempted to model the early solar system in an effort to test the “jumping-Jupiter” theory. Nesvorny found that Jupiter did in fact jump due to gravitational interactions from Uranus or Neptune, but when Jupiter jumped, either Uranus or Neptune were expelled from the solar system. “Something was clearly wrong,” he said.

Based on his early results, Nesvorny added a fifth giant planet, similar to Uranus or Neptune to his simulations. Once he ran the reconfigured simulations, everything fell into place. The simulation showed the fifth planet ejected from the solar system by Jupiter, with four giant planets remaining, and the inner, terrestrial planets untouched.

Nesvorny concluded with, “The possibility that the solar system had more than four giant planets initially, and ejected some, appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, indicating the planet ejection process could be a common occurrence.”

If you’d like to read Nesvorny’s full paper, you can access it at: http://arxiv.org/pdf/1109.2949v1

Source: Southwest Research Institute Press Release