Posted on by Elizabeth Howell

‘Vulnerable’ Earth-Like Planets Could Survive With Friction: Study

Flexible planets: NASA is studying how planets in eccentric orbits flex due to tidal forces. At left is a planet with a thick ice shell, and at right a terrestrial-type planet. Credit: NASA's Goddard Space Flight Center

If you’re a potentially habitable world orbiting in a zone where liquid water can exist — and then a rude gas giant planet happens to disturb your orbit — that could make it difficult or impossible for life to survive.

But even in the newly eccentric state, a new study based on simulations shows that the orbit can be made more circular again quite quickly, taking only a few hundred thousand years to accomplish. The key is the tidal forces the parent star exerts on the planet as it moves in its orbit, flexing the interior and slowing the planet down to a circular orbit.

“We found some unexpected good news for planets in vulnerable orbits,” stated Wade Henning, a University of Maryland scientist who led the work and who is working at NASA’s Goddard Space Flight Center in Maryland. “It turns out these planets will often experience just enough friction to move them out of harm’s way and into safer, more-circular orbits more quickly than previously predicted.“

The transition period wouldn’t be pretty, since NASA states the planets “would be driven close to the point of melting” or have a “nearly melted layer” on them. The interior could also host magma oceans, depending on how intense the friction is. But a softer planet flexes more easily, allowing it to generate heat, bleed that energy off into space and gradually settle into a circular orbit. When tidal heating ceases, then life could possibly take hold.

This artists' rendition shows a super-Earth, or low mass exoplanet, orbiting close to its parent star. Credit: Keck Observatory
This artists’ rendition shows a super-Earth, or low mass exoplanet, orbiting close to its parent star. Credit: Keck Observatory

Another possibility is the eccentric orbit itself may be enough to keep life happy, at least for a while. If the planet is colder and stiffer, and orbiting far from its star, it’s possible the tidal flexing would serve as an energy source for life to survive.

Think of a situation like Europa near Jupiter, where some scientists believe the moon could have a subsurface ocean heated by interactions with the gas giant.

The model covers planets that are between the size of Earth and 2.5 times larger, and future studies will aim to see how layers in the planet change over time.

Source: NASA

Posted on by Jason Major

A New Image of Europa Emerges

Europa's icy, cracked surface imaged by NASA's Galileo spacecraft Credit: NASA/JPL-Caltech/SETI Institute

Eureka – it’s Europa! And a brand-new image of it, too! (Well, kinda sorta.)

The picture above, showing the icy moon’s creased and cracked surface, was made from images acquired by NASA’s Galileo spacecraft during its exploration of Jupiter and its family of moons in 1997 and 1998. While the data itself isn’t new per se the view seen here has never been released by JPL, and so it’s new to you! (And to me too.)

Europa's bizarre surface features suggest an actively churning ice shell above a salty liquid water ocean. Credit: JPL
Europa’s bizarre surface features suggest an actively churning ice shell above a salty liquid water ocean. Credit: JPL

The original high-resolution images were acquired on Nov. 6, 1997, in greyscale and colorized with data acquired during a later pass by Galileo in 1998. The whiter areas are regions of relatively pure water ice, while the rusty red bands are where ice has mixed with salts and organic compounds that have oozed up from deeper within Europa.

Read more: Hydrogen Peroxide Could Feed Life on Europa

The entire image area measures about 101 by 103 miles across (163 km x 167 km).

Europa has long been one of the few places we know of outside our own planet where life could very well have evolved and potentially still exist. Getting a peek below the icy moon’s frozen crust — or even a taste of the recently-discovered water vapor spraying from its south pole — is all we’d need to further narrow down the chances that somewhere, something could be thriving in Europa’s subsurface seas. Get a planetary scientist’s perspective in a video interview with Dr. Mike Brown here.

Launched in October 1989, the Galileo spacecraft arrived at Jupiter in December 1995. Through primary and extended missions Galileo explored the giant planet and its family of moons until plunging into Jupiter’s atmosphere on September 21, 2003. Learn more about Galileo here, and check out some of the amazing images it acquired on the CICLOPS imaging diary page here.

Source: NASA’s Planetary Photojournal

Posted on by Elizabeth Howell

An Ocean On Pluto’s Moon? Hopeful Scientists Will Keep An Eye Out For Cracks

Artist impression of Pluto and Charon (NASA)

It’s a lot of speculation right now, but the buzz in a new NASA study is Pluto’s largest moon (Charon) could have a cracked surface.

If the New Horizons mission catches these cracks when it whizzes by in 2015, this could hint at an ocean underneath the lunar surface — just like what we talk about with Europa (near Jupiter) and Enceladus (near Saturn). But don’t get too excited — it’s also possible Charon had an ocean, but it froze out over time.

“Our model predicts different fracture patterns on the surface of Charon depending on the thickness of its surface ice, the structure of the moon’s interior and how easily it deforms, and how its orbit evolved,” stated Alyssa Rhoden of NASA’s Goddard Space Flight Center in Maryland, who led the research.

“By comparing the actual New Horizons observations of Charon to the various predictions, we can see what fits best and discover if Charon could have had a subsurface ocean in its past, driven by high eccentricity.”

It seems an unlikely proposition given that Pluto is so far from the Sun — about 29 times further away than the Earth is. Its surface temperature is -380 degrees Farhenheit (-229 degrees Celsius), which — to say the least — would not be a good environment for liquid water on the surface.

But it could happen with enough tidal heating. To back up, both Europa and Enceladus are small moons fighting gravity from their much larger gas giant planets, not to mention a swarm of other moons. This “tug-of-war” not only makes their orbits eccentric, but creates tides that change the interior and the surface, causing the cracks. Perhaps this might have kept subsurface oceans alive on these moons.

Encaladus, a moon of Saturn, as shown in this Voyager 1 image. Credit: NASA
Encaladus, a moon of Saturn, as shown in this Voyager 1 image. Credit: NASA

Since Charon once had an eccentric orbit, perhaps it also had tidal heating. Scientists think that the moon was created after a large object smacked into Pluto and created a chain of debris (similar to the leading theory for how our Moon was formed). The proportionally huge Charon — it’s one-eighth Pluto’s mass — would have been close to its parent planet, causing gravity to tug on both objects and creating friction inside their interiors.

“This friction would have also caused the tides to slightly lag behind their orbital positions,” NASA stated. “The lag would act like a brake on Pluto, causing its rotation to slow while transferring that rotational energy to Charon, making it speed up and move farther away from Pluto.”

But this friction would have ceased long ago, given that observations show Charon orbits in a stable circle further away from Pluto, and there are no extraneous tugs on its path today. So another possibility is there was an ocean beneath the moon’s surface that today is a block of ice.

The study was published in April in the journal Icarus. And by the way, some have even speculated that Pluto itself could have an ocean.

Source: NASA

Posted on by Shannon Hall

NASA Seeks Ideas for Mission to Europa

Jupiter's icy moon: Europa. Image Credit: NASA

Europa — a moon of Jupiter first discovered by Galileo — never ceases to surprise and amaze astronomers and amateurs alike.

Last December astronomers announced water plumes erupting 100 miles high from the moon’s icy south pole. It was the best evidence yet that Europa, heated internally by the powerful tidal forces generated by Jupiter’s gravity, has a deep subsurface ocean. It caused the search for life in the outer solar system to take quite a turn.

Now, NASA has issued a Request for Information (RFI) to science and engineering communities for ideas for a mission to the enigmatic moon. Any ideas need to address fundamental questions about the subsurface ocean and the search for life beyond Earth.

“This is an opportunity to hear from those creative teams that have ideas on how we can achieve the most science at minimum cost,” said John Grunsfeld, associate administrator for the NASA Science Mission Directorate, in a press release.

The RFI’s focus is for concepts for a mission that costs less than $1 billion.

“Europa is one of the most interesting sites in our solar system in the search for life beyond Earth,” said Grunsfield. “The drive to explore Europa has stimulated not only scientific interest but also the ingenuity of engineers and scientists with innovative concepts.”

The Decadal Survey deemed a mission to Europa as an extremely high priority for scientific pursuits by NASA. It lists five key science objectives that are necessary to improve our understanding of this potentially habitable moon. Primarily, the mission will need to:

— Characterize the extent of the ocean and its relation to the deeper interior

— Characterize the ice shell and any subsurface water, including their heterogeneity, and the nature of surface-ice-ocean exchange

— Determine global surface, compositions and chemistry, especially as related to habitability

— Understand the formation of surface features, including sites of recent or current activity, identify and characterize candidate sites for future detailed exploration

— Understand Europa’s space environment and interaction with the magnetosphere.

Although Europa has been visited by spacecraft and imaged distantly by Hubble, more detailed research is necessary to understand the complexities of this moon and its potential for life. NASA’s Galileo spacecraft, launched in 1989 was the only mission to visit Europa, passing close by the moon fewer than a dozen times.

What are your ideas for a mission to the icy moon? Comment below.

Posted on by Fraser Cain

Weekly Space Hangout – March 7, 2014: Cosmos Premiere & NASA Budget

Host: Fraser Cain
Astrojournalists: David Dickinson, Matthew Francis, Casey Dreier, Jason Major, Brian Koberlein, Alan Boyle

This week’s stories:

Alan Boyle (@b0yle, cosmiclog.com ):
Cosmos premiere!

David Andrew Dickinson (@astroguyz):
Watch the Close Pass of NEO 2014 DX110
Daylight Saving time: A Spring Forward or a Step Back?
A Natural Planetary Defense Against Solar Storms

Matthew Francis (@DrMRFrancis, BowlerHatScience.org):
Using gravitational lensing to measure a spinning quasar
CosmoAcademy classes

Casey Dreier (Planetary.org):
The 2015 NASA Budget Request
NASA Kinda Embraces Exploring Europa

Jason Major (@JPMajor, LightsInTheDark.com):
That’s the way the asteroid crumbles

Brian Koberlein (@briankoberlein, briankoberlein.com):
*Possible* evidence for dark matter WIMPs
Black Holes exceed Eddington limit
Using quasars in a quantum experiment

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

Posted on by Fraser Cain

Why Europa?

This artist's rendering shows NASA's Europa Clipper spacecraft, which is scheduled to launch in October, 2024. It'll have to contend with Jupiter's powerful radiation. Will a newly-found low-radiation path to Europa help? Image Credit: NASA/JPL

Forget Mars, the place we really want to go looking for life is Jupiter’s moon Europa. Dr. Mike Brown, a professor of planetary science at Caltech, explains what he finds so fascinating about this icy moon, and the potential we might find life swimming in its vast oceans.
Continue reading “Why Europa?”

Posted on by Fraser Cain

What Are Cassini’s Most Interesting Discoveries?

What Are Cassini's Most Interesting Discoveries?

We recently interviewed Dr. Kevin Grazier, on of the scientist who has worked extensively on the Cassini mission. Here’s what he had to tell us about that mission’s discoveries.

“My name is Kevin Grazier. I am a planetary scientist, and for my research I do long-term integrations or simulations of early solar system evolution. I’m a former scientist on the Cassini mission and a consultant to several TV series such as Defiance, Falling Skies, the movie Gravity, and formerly, Battlestar Galactica.”

What are Cassini’s most amazing discoveries?
“Cassini has essentially rewritten the book on the Saturn system. I was on the spacecraft team for 15 years. I worked as a science planner and as the Investigation Scientist on the ISS instrument. (That’s Imaging Science Subsystem, not International Space Station.) And of the discoveries we found, I’m trying to think of what I’d call or classify as the most exciting.”

“One was predicted – the fact that it was believed that there could be ice volcanoes on Enceladus. And as a matter of fact, there are volcanoes on Enceladus, or active venting, however you want to look at that. Those vents create the “E” ring, so we have a ring created by material vented off Enceladus. That’s pretty exciting, because we see an active object venting material, and there aren’t a lot of active objects in the solar system.”

This mosaic of Titan was created from the first flyby of the moon by Cassini in 2004. Credit: NASA/JPL/SS
This mosaic of Titan was created from the first flyby of the moon by Cassini in 2004. Credit: NASA/JPL/SS

“The surface of Titan is really fantastic. We have open oceans or seas of hydrcarbons on Titan. We have the possibility of an open ocean underneath the crust, just like we believe is under the surface of Europa. We have one image which seems to capture what might be a volcanic eruption. That’s important, because in the outer solar system, planetary science considers ice a rock. What a rock is defined as depends on where you are in the solar system. So in the outer solar system, ice is a rock. All of the moons in the outer solar system except Io have icy crusts. Now, if you have a volcanic eruption on Titan, we have an eruption of magma, and if ice is a rock, that eruption is water. So we have evidence of magma chambers which could be cauldrons of life-giving water.”

“How cool is that? How counter-intuitive is that? How science-fiction-y is that? That one of the most interesting places to look for is a lava chamber or magma chamber that could be suitable for sustaining life. I think that’s really exciting.”

You can follow Dr. Kevin on Twitter

Posted on by Shannon Hall

Lithopanspermia: How Earth May Have Seeded Life on Other Solar System Bodies

The theory of Lithopanspermia states that life can be shared between planets within a planetary system. Credit: NASA

With the recent discovery that Europa has geysers, and therefore definitive proof of a liquid ocean, there’s a lot of talk about the possibility of life in the outer solar system.

According to a new study, there is a high probably that life spread from Earth to other planets and moons during the period of the late heavy bombardment — an era about 4.1 billion to 3.8 billion years ago — when untold numbers of asteroids and comets pummeled the Earth. Rock fragments from the Earth would have been ejected after a large meteoroid impact, and may have carried the basic ingredients for life to other solar system bodies.

These findings, from Pennsylvania State University, strongly support lithopanspermia: the idea that basic life forms can be distributed throughout the solar system via rock fragments cast forth by meteoroid impacts.

Strong evidence for lithopanspermia is found within the rocks themselves. Of the over 53,000 meteorites found on Earth, 105 have been identified as Martian in origin. In other words an impact on Mars ejected rock fragments that then hit the Earth.

The researchers simulated a large number of rock fragments ejected from the Earth and Mars with random velocities. They then tracked each rock fragment in n-body simulations — models of how objects gravitationally interact with one another over time — in order to determine how the rock fragments move among the planets.

“We ran the simulations for 10 million years after the ejection, and then counted up how many rocks hit each planet,” said doctoral student Rachel Worth, lead author on the study.

Their simulations mainly showed a large number of rock fragments falling into the Sun or exiting the solar system entirely, but a small fraction hit planets. These estimations allowed them to calculate the likelihood that a rock fragment might hit a planet or a moon. They then projected this probability to 3.5 billion years, instead of 10 million years.

In general the number of impacts decreased with the distance away from the planet of origin. Over the course of 3.5 billion years, tens of thousands of rock fragments from the Earth and Mars could have been transferred to Jupiter and several thousand rock fragments could have reached Saturn.

“Fragments from the Earth can reach the moons of Jupiter and Saturn, and thus could potentially carry life there,” Worth told Universe Today.

The researchers looked at Jupiter’s Galilean satellites: Io, Europa, Ganymede and Callisto and Saturn’s largest moons: Titan and Enceladus. Over the course of 3.5 billion years, each of these moons received between one and 10 meteoroid impacts from the Earth and Mars.

It’s statistically possible that life was carried from the Earth or Mars to one of the moons of Jupiter or Saturn. During the period of late bombardment the solar system was much warmer and the now icy moons of Saturn and Jupiter didn’t have those protective shells to prevent meteorites from reaching their liquid interiors. Even if they did have a thin layer of ice, there’s a large chance that a meteorite would fall though, depositing life in the ocean beneath.

In the case of Europa, six rock fragments from the Earth would have hit it over the last 3.5 billion years.

It has previously been thought that finding life in Europa’s oceans would be proof of an independent origin of life. “But our results suggest we can’t assume that,” Worth said. “We would need to test any life found and try to figure out whether it descended from Earth life, or is something really new.”

The paper has been accepted for publication in the journal Astrobiology and is available for download here.