News from Space: Titan’s Seas Mapped in Detail

titan_cassiniIt’s been an eventful year for NASA, thanks to the ongoing efforts of its many space probes and landers. In addition to some breathtaking discoveries made on Mars (proof of the existence of water and an atmosphere in the past), the MESSENGER probe discovered ice around the poles of Mercury, captured impressive footage of the surface, and mapped out the planet for the first time.

And while all this was happening in the Inner Solar System, the Cassini space probe was doing some rather impressive things in the Outer Solar System. In addition to taking part in the “Smile at Saturn” event, surveying the Jovian satellite of Europa, and unlocking the strange secrets of Saturn’s moons, Cassini also provided the most detailed map yet of the Saturnalian giant known as Titan.

titan_surfaceAnd now, using the data provided by NASA’s spacecraft, scientists have created this beautiful mosaic mapping the northern hemisphere of Titan, which is full of rivers, lakes, and seas. Ever since Cassini started mapping the world in 2004, it has been known that Titan boasts natural bodies of water that are composed not of water, but liquid hydrocarbons.

However, Cassini’s scans missed the true extent of some seas, including the biggest one of all: Kraken Mare. This new map fills in almost all the area of Titan’s north pole and provides scientists with important answers to some of their questions. These include how the geographic distribution of these natural bodies of water came to be.

titan_surface1For instance, while the northern hemisphere is dotted all over with hundreds of tiny lakes, the large seas seem confined to a specific area (see the lower right side of the image above). As geophysicist Randolph Kirk of the U.S. Geological Survey pointed out during a press conference at the American Geophysical Union conference, geological forces are most likely at work here.

Basically, the team thinks that Titan’s crust has fractured here when active tectonics created almost straight lines of parallel mountain chains. The low-lying areas are what gets filled with liquid, creating Kraken Mare and its smaller neighbor, Ligeia Mare. The scientists think the process may be analogous to the flooding which created large bodies of water in Nevada some 12,000 years ago.

titan_lakesOther tectonic processes are probably behind the smaller dotted lakes too, though scientists don’t yet know precisely what. Some of the lakes could be the infilled calderas of former active volcanoes, which would spew molten water instead of lava. But there isn’t enough volcanic activity on the moon to account for all of them.

Instead, many were probably created when liquid hydrocarbons dissolved the frozen ice, in the same way that water on Earth dissolves limestone to create features like the Bottomless Lakes in New Mexico. According to Kirk, “this creates a kind of exciting prospect that under the northern pole of Titan is a network of caves.” Such caves on Earth are often filled with all manner of life, so these ones could be as well.

Moons_of_Saturn_2007Other radar data has shown the depth and volume of Ligeia Mare, the second largest sea in the northern hemisphere. According to NASA scientists, the sea has a maximum depth of about 170 meters, as deep as Lake Michigan, and about twice its volume. Alas, beyond the comparative size of these bodies of water, Titan’s liquid bodies could not be more different than those on Earth.

As already noted, Titan’s lakes, rivers and seas are composed of liquid hydrocarbons, most likely ethane and methane. Ordinarily, these exist in gaseous form. But given Titan’s surface conditions, where the average temperatures is -180 degrees Celsius (-292 Fahrenheit), these hydrocarbons are able to exist in liquid form.

TitanNevertheless, finding evidence of such chemicals on planets beyond Earth is a rare and impressive find. Combined with the discovery of propelyne in Titan’s atmosphere – an organic compound that is a byproduct of oil refining, fossil fuel extraction, and thought not to exist beyond Earth – this moon is proving to be full of surprises!

And be sure to enjoy this video which simulates a flyover of Titan, as complied by NASA from the data provided by the Cassini space probe:


News From Space: 200 km Water Jets on Europa

europa-landerAs the prime candidate for extra-terrestrial life, the Jovian moon of Europa has been the subject of much speculation and interest over years. And while our understanding of the surface has improved – thanks to observations made by several space probes and the Hubble space telescope – what lies beneath remains a mystery. Luckily, Europa may yet provide Earth scientists with a chance to look at its interior.

Earlier this month, data collected from the Hubble space telescope suggested that enormous jets of water more than 200 kilometers tall may be spurting intermittently from the moon’s surface. The findings, presented last week to the American Geophysical Union, await independent confirmation. But if the jets are real, the frozen world would join the tiny number of others known to have active jets, including Saturn’s moon Enceladus and Neptune’s moon Triton.

europa-lander-2What’s more, should these newly observed water plumes be tapping into some Europan sea, they could be bringing material to the surface that would otherwise stay hidden. Follow-up observations from Earth or with probes around Europa could sample the fountains, hunting for organic material and perhaps finding the evidence need to prove that living organisms exist beyond Earth.

Scientists spotted the plumes thanks to ultraviolet images taken by Hubble in December 2012. The research team, which hails from the Southwest Research Institute in Texas, then published their research in Science magazine. In the paper, astronomer and co-author Lorenz Roth explained their findings:

We found that there’s one blob of emission at Europa’s south pole. It was always there over the 7 hours we observed and always at the same location.

Previous observations from NASA’s Galileo mission, which visited the Jupiter system in the 1990s and early 2000s, suggest that Europa’s south pole is full of ridges and cracks quite similar to features called tiger stripes on Enceladus that spew water.

europa_chaosterrainLorenz and his team looked back through previous Hubble data to see if the plumes could have been spotted earlier but saw nothing, suggesting that they are likely transient. At the time, Europa was at its farthest from Jupiter, which could explain why the jets appeared only then. Researchers recently determined that Enceladus’ plumes are weakest when the moon is closest to Saturn, likely because the ringed planet’s gravity squeezes the tiger stripes shut.

Astronomer Kurt Retherford, also of SwRI and another co-author, claimed that the case of Enceladus helped them to make a connection with what they were observing:

We actually saw this press release on Enceladus. And we thought, ‘Oh my god! This is the explanation’” for why Europa’s plumes might only appear when it’s far from Jupiter.

In the past, scientists have looked for evidence of jets coming from Europa’s surface. When the Voyager probes flew by in the 70s, one image showed a fuzzy spot that some thought to be a plume, though most considered it an artifact of imaging. Galileo also saw a row of dark spots on a ridge of Europa which looked similar to spots seen on planet Earth before an eruption begins.

europaBecause of these previous false positives though, scientists are likely to be cautious when interpreting these newest results. But even with these reservations, Robert Pappalardo – who leads the planning team for the Europa Clipper Pre-Project (a proposed mission to Europa) – said that he’s already discussing with other scientists how these new results should affect their study priorities.

For instance, some future orbiter headed to Europa could carry detectors specifically designed to search for heavy organic molecules that could be indicative of life in the subsurface. When it passed over the geyser’s spray, it would be bathed in material from the moon’s interior, giving scientists a window into Europa’s ocean. Pappalardo also hopes that the finding will help push Europa to a place of high priority in NASA’s exploration agenda.

Due to budget constraints, a manned mission is not yet feasible, but NASA has indicated that it would be willing to send a robot lander there in the near future. In addition, recent computer models provided from the University of Texas showed that the ice is likely to be thinnest at the equator. Between the possibility that the oceans might be most accessible in this region, and the likelihood that some of that water escapes into space, unlocking the mysteries of the Jovian satellite might be easier than previously thought.