Posted on by Jason Major

The Flip Side of Exoplanet Orbits

New research reveals the possible cause of retrograde "hot Jupiters"

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It was once thought that our planet was part of a “typical” solar system. Inner rocky worlds, outlying gas giants, some asteroids and comets sprinkled in for good measure. All rotating around a central star in more or less the same direction. Typical.

But after seeing what’s actually out there, it turns out ours may not be so typical after all…

Astronomers researching exoplanetary systems – many discovered with NASA’s Kepler Observatory – have found quite a few containing “hot Jupiters” that orbit their parent star very closely. (A hot Jupiter is the term used for a gas giant – like Jupiter – that resides in an orbit very close to its star, is usually tidally locked, and thus gets very, very hot.) These worlds are like nothing seen in our own solar system…and it’s now known that some actually have retrograde orbits – that is, orbiting their star in the opposite direction.

“That’s really weird, and it’s even weirder because the planet is so close to the star. How can one be spinning one way and the other orbiting exactly the other way? It’s crazy. It so obviously violates our most basic picture of planet and star formation.”

– Frederic A. Rasio, theoretical astrophysicist, Northwestern University

Now retrograde movement does exist in our solar system. Venus rotates in a retrograde direction, so the Sun rises in the west and sets in the east, and a few moons of the outer planets orbit “backwards” relative to the other moons. But none of the planets in our system have retrograde orbits; they all move around the Sun in the same direction that the Sun rotates. This is due to the principle of conservation of angular momentum, whereby the initial motion of the disk of gas that condensed to form our Sun and afterwards the planets is reflected in the current direction of orbital motions. Bottom line: the direction they moved when they were formed is (generally) the direction they move today, 4.6 billion years later. Newtonian physics is okay with this, and so are we. So why are we now finding planets that blatantly flaunt these rules?

The answer may be: peer pressure.

Or, more accurately, powerful tidal forces created by neighboring massive planets and the star itself.

By fine-tuning existing orbital mechanics calculations and creating computer simulations out of them, researchers have been able to show that large gas planets can be affected by a neighboring massive planet in such a way as to have their orbits drastically elongated, sending them spiraling closer in toward their star, making them very hot and, eventually, even flip them around. It’s just basic physics where energy is transferred between objects over time.

It just so happens that the objects in question are huge planets and the time scale is billions of years. Eventually something has to give. In this case it’s orbital direction.

“We had thought our solar system was typical in the universe, but from day one everything has looked weird in the extrasolar planetary systems. That makes us the oddball really. Learning about these other systems provides a context for how special our system is. We certainly seem to live in a special place.”

– Frederic A. Rasio

Yes, it certainly does seem that way.

The research was funded by the National Science Foundation. Details of the discovery are published in the May 12th issue of the journal Nature.

Read the press release here.

Main image credit: Jason Major. Created from SDO (AIA 304) image of the Sun from October 17, 2010 (NASA/SDO and the AIA science team) and an image of Jupiter taken by the Cassini-Huygens spacecraft on October 23, 2000 (NASA/JPL/SSI).

Posted on by Jason Major

A Cometary Case for Titan’s Atmosphere

Ancient comets may have created Titan's nitrogen-rich atmosphere

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Titan is a fascinating world to planetary scientists. Although it’s a moon of Saturn it boasts an opaque atmosphere ten times thicker than Earth’s and a hydrologic cycle similar to our own – except with frigid liquid methane as the key component instead of water. Titan has even been called a living model of early Earth, even insofar as containing large amounts of nitrogen in its atmosphere much like our own. Scientists have wondered at the source of Titan’s nitrogen-rich atmosphere, and now a team at the University of Tokyo has offered up an intriguing answer: it may have come from comets.

Traditional models have assumed that Titan’s atmosphere was created by volcanic activity or the effect of solar UV radiation. But these rely on Titan having been much warmer in the past than it is now…a scenario that Cassini mission scientists don’t think is the case.

New research suggests that comet impacts during a period called the Late Heavy Bombardment – a time nearly 4 billion years ago when collisions by large bodies such as comets and asteroids were occurring regularly among worlds in our solar system – may have generated Titan’s nitrogen atmosphere. By firing lasers into ammonia-and-water-ice material similar to what would have been found on primordial Titan, researchers saw that nitrogen was a typical result. Over the millennia these impacts could have created enough nitrogen to cover the moon in a dense haze, forming the thick atmosphere we see today.

“We propose that Titan’s nitrogen atmosphere formed after accretion, by the conversion from ammonia that was already present on Titan during the period of late heavy bombardment about four billion years ago.”

– Yasuhito Sekine et al., University of Tokyo, Japan

This model, if true, would also mean that the source of Titan’s nitrogen would be different than that of other outer worlds, like Pluto, and even inner planets like our own.

See the published results in the journal Nature, or read more on NewScientist.com.

Top image is a combination of a color-composite of Titan made from raw Cassini data taken on October 12, 2010 and a recolored infrared image of the comet Siding Spring, taken by NASA’s WISE observatory on January 10, 2010. The background stars were also taken by the Cassini orbiter. NASA / JPL / SSI and Caltech/UCLA. Edited by J. Major.

Note: the image at top is not scientifically accurate…the comet’s tail would be, based on the lighting of Titan, pointing more to the ten o’clock position as well as forward toward the viewer’s left shoulder. This would make it ‘look’ as if it were going the opposite direction though, away from Titan, and so I went with the more immediately decipherable version seen here. To see a more “realistic” version, click here.

Posted on by Jason Major

More Evidence of Liquid Erosion on Mars?

Possible water-formed gullies cut through sedimentary layers in Terby Crater

 

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Terby Crater, a 170-km-wide (100-mile-wide) crater located on the northern edge of the vast Hellas Planitia basin in Mars’ southern hemisphere, is edged by variable-toned layers of sedimentary rock – possibly laid down over millennia of submersion beneath standing water. This image (false-color) from the HiRISE camera aboard the Mars Reconnaissance Orbiter shows a portion of Terby’s northern wall with what clearly looks like liquid-formed gullies slicing through the rock layers, branching from the upper levels into a main channel that flows downward, depositing a fan of material at the wall’s base.

But, looks can be deceiving…

 

Terby Crater. Credit: NASA/JPL/University of Arizona

Dry processes – especially on Mars, where large regions have been bone-dry for many millions of years – can often create the same effects on the landscape as those caused by running water. Windblown Martian sand and repetitive dry landslides can etch rock in much the same way as liquid water, given enough time. But the feature seen above in Terby seem to planetary scientists to be most likely the result of liquid erosion… especially considering that the sedimentary layers themselves seem to contain clay materials, which only form in the presence of liquid water. Is it possible that some water existed beneath Mars’ surface long after the planet’s surface dried out? Or that it’s still there? Only future exploration will tell for sure.

“While formation by liquid water is one of the proposed mechanisms for gully formation on Mars, there are others, such as gravity-driven mass-wasting (like a landslide) that don’t require the presence of liquid water. This is still an open question that scientists are actively pursuing.”

– Nicole Baugh, HiRISE Targeting Specialist

Terby Crater was once on the short list of potential landing sites for the new Mars Science Laboratory (aka Curiosity) rover but has since been removed from consideration. Still, it may one day be visited by a future robotic mission and have its gullies further explored from ground level.

Click here to see the original image on the HiRISE site.

Image credit: NASA / JPL / University of Arizona

Posted on by Jason Major

USPS Commemorates Spaceflight Past and Present

Postage stamps honoring Mercury astronaut Alan Shepard, America’s first man in space, and NASA’s MESSENGER probe, the first spacecraft to orbit Mercury, will be presented on May 4th at a public event taking place at the Aviation Heritage Park in Dayton, Ohio.

Alan Shepard poses in his pressure suit before his historic flight on May 5, 1961. Credit: NASA.

The first stamp salutes NASA’s Project Mercury, America’s first manned spaceflight program, and astronaut Alan B. Shepard, Jr.’s historic sub-orbital flight on May 5, 1961 aboard the spacecraft Freedom 7.

The other stamp highlights NASA’s MESSENGER spacecraft currently exploring the planet Mercury. It successfully established orbit around the planet on March 18, 2011, the first spacecraft ever to do so.

These two historic missions frame a remarkable fifty-year period in which the U.S. has advanced space exploration through more than 1,500 manned and unmanned flights.

Both stamps were designed by professional artist Donato Giancola of Brooklyn, NY, who based the stamp designs on NASA photos and images.

Both stamps will be issued as “Forever Stamps” for use in mailing a one-ounce letter. Regardless of when the stamps are purchased and no matter how postage prices may change, these stamps will always be equal to the current First-Class Mail one-ounce price.

NASA's Mercury-Redstone 3 rocket, with Alan Shepard inside the Freedom 7 capsule, launches from Cape Canaveral on May 5, 1961. Credit: NASA.

Stamps are now available online at the US Postal Service store here.

Posted on by Jason Major

A New Spin on Galactic Evolution

Spiral galaxy arms may carry stars along with them, suggests new study

 

There’s a new concept in the works regarding the evolution of galactic arms and how they move across the structure of spiral galaxies. Robert Grand, a postgraduate student at University College London’s Mullard Space Science Laboratory, used new computer modeling to suggest that these signature features of spiral galaxies – including our own Milky Way – evolve in different ways than previously thought.

The currently accepted theory is as spiral galaxies rotate, the “arms” are actually transient structures that move across the flattened disc of stars surrounding the galactic bulge, yet don’t directly affect the movement of the individual stars themselves. This would work in much the same way as a “wave” goes across a crowd at a stadium event. The wave moves, but the individual people do not move along with it – rather, they stay seated after it has passed.

However when Grand researched this suggested motion using computer models of galaxies, he and his colleagues found that this was not what tended to happen. Instead the stars actually moved along with the arms, rather than maintaining their positions.

Also it was observed in these models that the arms themselves are not permanent features, but rather break up and reform over the course of 80 to 100 million years. Grand suggests that this may be due to the powerful gravitational shear forces generated by the spinning of the galaxy.

“We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years. We found that stars are able to migrate much more efficiently than anyone previously thought. The stars are trapped and move along the arm by their gravitational influence, but we think that eventually the arm breaks up due to the shear forces.”

– Robert Grand

Snapshots of face-on view of a simulated disc galaxy.

The computer models also showed that the stars along the leading edge of the arms tended to move inwards toward the galactic center while the stars lining the trailing ends were carried to the outer edge of the galaxy.

Since it takes hundreds of millions of years for a spiral galaxy to complete even just one single rotation, observing their evolution and morphology is impossible to do in real time. Researchers like Grand and his simulations are key to our eventual understanding of how these islands of stars formed and continue to shape themselves into the vast, varied structures we see today.

“This research has many potential implications for future observational astronomy, like the European Space Agency’s next corner stone mission, Gaia, which MSSL is also heavily involved in.  As well as helping us understand the evolution of our own galaxy, it may have applications for regions of star formation.”

– Robert Grand

The results were presented at the Royal Astronomical Society’s National Astronomy Meeting in Wales on April 20. Read the press release on the Royal Astronomical Society’s website here.

Top image: M81, a spiral galaxy similar to our own Milky Way, is one of the brightest galaxies that can be seen from Earth. The spiral arms wind all the way down into the nucleus and are made up of young, bluish, hot stars formed in the past few million years, while the central bulge contains older, redder stars. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Posted on by Jason Major

Ride Along with Rhea

Animation made from raw Cassini image data acquired April 25, 2011

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Assembled from 29 raw images taken by the Cassini orbiter on Monday, April 25, this animation brings us along an orbital ride with Rhea as it crosses Saturn’s nighttime face, the planet’s shadow cast across the ringplane. Sister moons Dione and Tethys travel the opposite lane in the background, eventually appearing to sink into Saturn’s atmosphere.

Rhea's heavily cratered surface, imaged by Cassini on October 2010. NASA/JPL/SSI

The exposure varies slightly from frame to frame due to the fact that they are not all taken with the same color channel filter.

Rhea (1,528 kilometers, or 949 miles, wide), Dione (1,123 kilometers, or 698 miles wide) and Tethys (1,066 kilometers, or 662 miles wide) are all very similar in composition and appearance. The moons are composed mostly of water ice and rock, each covered in craters of all sizes and crisscrossed by gouges, scarps and chasms. All three are tidally locked with Saturn, showing the same face to their parent planet in the same way that the Moon does with Earth.

The Cassini spacecraft was 2,227,878 km (1,384,339 miles) from Rhea when the images were taken.

(The original images have not been validated or calibrated. Validated/calibrated images will be archived with the NASA Planetary Data System in 2012.)

Image credit: NASA / JPL / Space Science Institute. Animation by Jason Major.

Posted on by Jason Major

Mars’ Underground Atmosphere

Pitted "swiss cheese" terrain at Mars' south pole hints at sublimation of underground CO2

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Scientists have spotted an underground reservoir near Mars’ south pole the size of Lake Superior… except that this lake is filled with frozen carbon dioxide – a.k.a. “dry ice”!

A recent report by scientists at the Southwest Research Institute in Boulder, CO reveals variations in Mars’ axial tilt can change how much carbon dioxide gets released into the atmosphere, affecting factors from the stability of water on its surface to the power and frequency of dust storms.

Thickness Map of Buried CO2 Ice Deposit
Thickness Map of Buried CO2 Ice Deposit

The Mars Reconnaissance Orbiter’s ground-penetrating Shallow Radar identified a subsurface deposit of frozen material, confirmed as carbon dioxide ice by its radar signature and visual correlation to the surface pitting seen above. As the polar surface warms during the Martian spring, underground CO2 deposits evaporate (or “sublime”) leaving behind round depressions in the frozen ground. (This has been aptly dubbed “swiss cheese terrain” by researchers on the HiRISE imaging team.)

While scientists were aware of seasonal CO2 ice layers atop the water ice this new discovery brings to light nearly 30 times more frozen CO2 than was previously believed to exist. In fact this particular deposit alone contains 80% the amount of CO2 currently present in the planet’s entire atmosphere.

The importance of this finding is how the carbon dioxide ultimately affects the global Martian climate as it freezes and thaws. When the CO2 is frozen and locked away in subsurface deposits like this, it’s not free to enter the atmosphere and do what CO2 does best: warm the planet… as well as increase atmospheric pressure. This means that liquid water cannot last as readily on the surface since it will either freeze or boil away. Also with less air pressure the strength of wind is decreased, so dust storms are less frequent and less severe.

When factored in with the axial tilt difference – and thus variations in the amount of sunlight hitting the poles – researchers’ models show that Mars’ average atmospheric pressure may at times be 75% higher than it is today.

These shifts in the orientation of the Red Planet’s axis occur on 100,000-year intervals… long by human standards but geologically very frequent. Mars may have had liquid water existing on its surface fairly recently!

Mars' south polar ice cap, seen in April 2000 by Mars Odyssey. NASA/JPL/MSSS

Although this may sound that Mars has had its own share of global warming due to CO2 emissions in its history, it must be remembered that Mars and Earth have very different atmospheric compositions. Earth’s atmosphere is much thicker and denser than Mars’, so even when doubling its CO2 content Mars’ atmosphere is still too thin and dry to create a strong greenhouse effect… especially considering that the polar caps on Mars increase cooling more than additional CO2 in the atmosphere raises global temperature. Without oceans and atmosphere to collect and distribute heat, the effect of any warming quickly radiates out into space…and eventually the planet swings back into a freeze-dried state.

“Unlike Earth, which has a thick, moist atmosphere that produces a strong greenhouse effect, Mars’ atmosphere is too thin and dry to produce as strong a greenhouse effect as Earth’s, even when you double its carbon-dioxide content.”

– Robert Haberle, planetary scientist at NASA’s Ames Research Center

Read the full news release on the NASA Missions site.

Image credit: NASA / JPL / University of Arizona

 

Posted on by Jason Major

More Surprises From Pluto

Artist's illustration of Pluto's surface. Credit: NASA

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Ah, Pluto. Seems every time we think we’ve got it figured out, it has a new surprise to throw at us.

First spotted in 1930 by a young Clyde Tombaugh, for 76 years it enjoyed a comfortable position as the solar system’s most distant planet. Then a controversial decision in 2006 by the International Astronomical Union, spurred by suggestions from astronomer (and self-confessed “planet-killer”) Mike Brown*, relegated Pluto to a new class of worlds called “dwarf planets”. Not quite planets and not quite asteroids, dwarf planets cannot entirely clear their orbital path with their own gravitational force and thus miss out on full planetary status. Besides immediately making a lot of science textbooks obsolete and rendering the handy mnemonic “My Very Eager Mother Just Served Us Nine Pies” irrelevant (or at least confusing), the decision angered many people around the world, both in and out of the scientific community. Pluto is a planet, they said, it always has been and always will be! Save Pluto! the schoolkids wrote in crayon to planetarium directors. The world all of a sudden realized how much people liked having Pluto as the “last” planet, and didn’t want to see it demoted by decision, especially a highly contested one.

Yet as it turns out, Pluto really may not be a planet after all.

It may be a comet.

But…that’s getting ahead of ourselves. First things first.

Discovery data showing carbon monoxide spectrum. Credit: J.S. Greaves / Joint Astronomy Centre.

Recent discoveries by a UK team of astronomers points to the presence of carbon monoxide in Pluto’s atmosphere. Yes, Pluto has an atmosphere; astronomers have known about it since 1988. At first assumed to be about 100km thick, it was later estimated to extend out about 1500km and be composed of methane gas and nitrogen. This gas would expand from the planet’s – er, dwarf planet’s – surface as it came closer to the Sun during the course of its eccentric 248-year orbit and then freeze back onto the surface as it moved further away. The new findings from the University of St Andrews team, made by observations with the James Clerk Maxwell telescope in Hawaii, identify an even thicker atmosphere containing carbon monoxide that extends over 3000 km, reaching nearly halfway to Pluto’s largest moon, Charon.

It’s possible that this carbon monoxide atmosphere may have expanded outwards from Pluto, especially in the years since 1989 when it made the closest approach to the Sun in its orbit. Surface heating (and the term “heating” is used scientifically here…remember, at around -240ºC (-400ºF) Pluto would seem anything but balmy to us!) by the Sun’s radiation would have warmed the surface and expelled these gases outwards. This also coincides with observations made by the Hubble Space Telescope over the course of four years, which revealed varying patterns of dark and light areas on Pluto’s surface – possibly caused by the thawing of frozen areas that shift and reveal lighter surface material below.

“Seeing such an example of extra-terrestrial climate-change is fascinating. This cold simple atmosphere that is strongly driven by the heat from the Sun could give us important clues to how some of the basic physics works, and act as a contrasting test-bed to help us better understand the Earth’s atmosphere.”

–  Dr. Jane Greaves, Team Leader

In fact, carbon monoxide may be the key to why Pluto even still has an atmosphere. Unlike methane, which is a greenhouse gas, carbon monoxide acts as a coolant; it may be keeping Pluto’s fragile atmosphere from heating up too much and escaping into space entirely! Over the decades and centuries that it takes for Pluto to complete a single year, the balance between these two gases must be extremely precise.

Read more about this discovery on the Royal Astronomical Society’s site.

Pluto's elliptical orbit

So here we have Pluto exhibiting an expanding atmosphere of thawing expelled gas as it gets closer to the Sun in an elliptical, eccentric orbit. (Sound familiar?) And now there’s another unusual, un-planet-like feature that’s being put on the table: Pluto may have a tail.

Actually this is an elaboration of the research results coming from the same team at the University of St Andrews. The additional element here is a tiny redshift detected in the carbon monoxide signature, indicating that it is moving away from us in an unusual way. It’s possible that this could be caused by the top layers of Pluto’s atmosphere – where the carbon monoxide resides – being blown back by the solar wind into, literally, a tail.

That sounds an awful lot, to this particular astronomy reporter anyway, like a comet.

Just saying.

Anyway, regardless of what Pluto is or isn’t, will be called or used to be called, there’s no denying that it is a fascinating little world that deserves our attention. (And it will be getting plenty of that come July 2015 when the New Horizons spacecraft swings by for a visit!) I’m sure there’s no one here who would argue that fact.

New Horizons’ upcoming visit will surely answer many questions about Pluto – whatever it is – and most likely raise even more.

 

Artist's impression of Pluto's huge atmosphere of carbon monoxide.Credit:P.A.S. Cruickshank.

The new discovery was presented by team leader Dr. Jane Greaves on Wednesday, April 20 at the National Astronomy Meeting in Wales.

Article reference: arxiv.org/abs/1104.3014: Discovery Of Carbon Monoxide In The Upper Atmosphere Of Pluto

 

*No disrespect to Mr. Brown intended…he was just performing science as he saw fit!

 

 

Posted on by Jason Major

Red Suns and Black Trees: Shedding a New Light on Alien Plants

 

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The grass may definitely not be greener on some alien worlds, suggests a new study from the UK. For example, planets in double-star systems could have grey or black vegetation.

Researcher Jack O’Malley-James of the University of St Andrews in Scotland worked out how photosynthesis in plants is affected by the color of the light they receive. On Earth, most plants have evolved to be green in order to take advantage of the yellowish color of the sunlight that’s received on the surface of our planet. (Our Sun, classified as a “Population I yellow dwarf star”, would look bright white from space but our atmosphere makes it appear yellow.) There are lots of other stars like our Sun in the Universe, and many of them are in multiple systems sharing orbits with other types of stars…red dwarfs, blue stars, red giants, white dwarfs…stars come in many different colors depending on their composition, age, size and temperature. We may be used to yellow but nature really has no preference! (Although red dwarfs happen to be the garden variety star in our own galaxy.)

Terrestrial examples of dark-colored plants

Planets that orbit within these multiple systems and exist within the habitable “Goldilocks” zone (and we are finding more and more candidates every day!) could evolve plants that depend on suns with different colors than ours. Green does a good job powering photosynthesis here, but on a planet orbiting a red dwarf and Sun-like star plants could very well be grey or black to absorb more light energy, according to O’Malley-James.

“Our simulations suggest that planets in multi-star systems may host exotic forms of the more familiar plants we see on Earth. Plants with dim red dwarf suns for example, may appear black to our eyes, absorbing across the entire visible wavelength range in order to use as much of the available light as possible.”

– Jack O’Malley-James, School of Physics and Astronomy, University of St Andrews

The study takes into consideration many different combinations of star varieties and how any potential life-sustaining planets could orbit them.

In some instances different portions of a planet may be illuminated by a differently-colored star in a pair…what sorts of variations in plant (and subsequently, animal) evolution could arise then?

And it’s not just the colors of plants that could evolve differently. “For planets orbiting two stars like our own, harmful radiation from intense stellar  flares could lead to plants that develop their own UV-blocking sunscreens, or photosynthesizing microorganisms that can move in response to a sudden flare,” said O’Malley-James.

Kermit may have been right all along…being green might really not be easy!

Read more on the Royal Astronomical Society’s news release or on the University of St Andrews website.

Top image credit: Jason Major

Posted on by Jason Major

Is Titan Hiding an Ocean?

Titan holds yet more secrets, far beneath its haze...

 

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Saturn’s moon Titan just keeps throwing surprises at us. A multi-layered atmosphere thicker than our own? Check. A hydrologic cycle that relies on methane as the operating liquid? Check. Rivers, streams and lakes filled with this same liquid? Check, check and check. And now, scientists are suspecting that Titan may have yet another surprise: a subsurface ocean.

Observations of Titan’s rotation and orbit, carried out by researchers at the Royal Observatory of Belgium using Cassini data, point at an unusual rotational inertia; that is, its resistance to changes in its motion, also known as moment of inertia or angular mass. Basically Titan moves in a way that is not indicative of a solid body of its previously assumed density and mass. Rather, its motion – both around its own axis and in its tidally-locked orbit around Saturn – are more in line with an object that isn’t uniformly solid.

Titan's thick clouds hide its surface well. NASA / JPL / SSI / J.Major

According to the math, Titan may very well be filled with liquid!

Or, at least, have a liquid layer of considerable depth beneath its surface. How far below the surface, how deep and exactly what kind of liquid are all speculative at this point…it’s suggested that it may be a subsurface ocean of yet more methane. This would help answer the question of where Titan gets all of its methane in the first place; methane, – a.k.a. natural gas – is a compound that breaks down quickly in sunlight. In fact, the high-level haze that surrounds the moon like a wispy blue shell is made up of this broken-down methane. So if this stuff is raining down onto the surface in giant, frigid drops and filling streams and lakes, but is still being broken down by ultraviolet light from the Sun to enshroud the entire moon (Titan is BIG, remember…at 5,150 km – 3,200 miles – wide, it’s over a third the size of Earth!) then there has to be somewhere that this methane is coming from.

If these calculations are right, it may be coming from underground.

We propose a new Cassini state model for Titan in which we assume the presence of a liquid water ocean beneath an ice shell… with the new model, we find a closer agreement between the moment of inertia and the rotation state than for the solid case, strengthening the possibility that Titan has a subsurface ocean.

– Rose-Marie Baland et al.

Of course in order for this hypothesis to be proven many more numbers are going to have to be crunched and more data reviewed. And more possibilities considered, too; Titan’s orbital irregularities may in fact be the result of external forces, such as a close pass by a comet or other large body. Still, there’s something to be investigated here and you can bet there’ll be no shortage of attention on a problem as intriguing as this!

Titan may soon be joining the short list of moons speculated to possess subsurface oceans, alongside Jupiter’s Europa and Ganymede and sister Saturnian satellite Enceladus…and who knows how many others?

Read the article on MIT’s Physics arXiv Blog, or you can download the full report here.

Top image credit: NASA / JPL / SSI. (Edited by J. Major.)