Antarctic lake, ho! Nearly twenty years ago Russian scientists began drilling through the over two miles of ice above Lake Vostok, a gigantic underground lake in Antarctica that hasn’t seen the surface in 20 million years. The pristine lake was reached last week, prompting a flurry of discussion among scientists and members of the media about how the Russian team could keep from contaminating it and whether unusual microbial life would be found there. Kept warm and liquid by heat from the center of the Earth, Lake Vostok, the largest in a chain of about 200 underground (or under-ice) lakes, is similar to the oceans supposed to exist below the surface on moons Enceladus and Europa, which makes this an exciting time to be an astrobiologist. Or, really, anyone interested in the origins of life.
It can be hard to reconstruct in your head the long, drawn-out process of reaching the lake when poring over the recent news stories on this topic. But a nice graphic put together by Nature News gives a blow-by-blow: In 1990, scientists began drilling at Vostok Station, the Russians’ Antarctic base, returning every summer to continue the task. At first they were drilling to remove ice cores that would provide data on climate, but by the mid-1990s, scientists had realized that a huge lake was deep below the surface. To protect the lake from contamination by the drilling fluids, which include kerosene, the team agreed they would melt the last bit of ice using a thermal probe instead of the drill (we don’t know yet if they did in fact follow the plan). As they got deeper into the ice, the drill became stuck, but trying another route met with success on February 5th.
[via Nature News]
Image courtesy of Nature News, created from Lukin, V. & Bulat, S. Geophys. Monogr. Ser. 192, 187–197 (2011).
Carbonated oceans, moons torn apart, ring tsunamis—there’s a flurry of cool news about Saturn coming out of the American Astronomical Society’s Division for Planetary Science meeting in Pasadena, California.
The fizzy ocean of Enceladus
Saturn’s moon Enceladus is one of the prime candidates for some kind of life elsewhere in the solar system, thanks the the possibility that a large subsurface ocean feeds the plumes of ice and vapor that the Cassini spacecraft has spied blasting forth from the moon. At the AAS meeting in California, Cassini scientists Dennis Matson proposed something new about this extraterrestrial ocean: It could be carbonated.
Noncarbonated seawater circulating from the moon’s solid core to the surface would stall rather than seep though cracks in the ice because seawater is denser than the icy carapace. If the seawater were fizzy, however, gas bubbles would form in the liquid, reducing the ocean’s density. Once the seawater became less dense than the ice, the water could rise to within 10 to 15 meters of the frigid surface. That’s close enough to fill chambers in the icy crust with water that feeds the south polar plumes. [Science News]
There’s a lot more going on beneath those huge sheets of Antarctic ice than you might think. NASA researchers say they uncovered a major surprise in December: The team drilled an eight-inch hole and stuck a video camera 600 feet down, hoping to observe the underbelly of the thick ice sheet. To their amazement, a curious critter swam into view and clung to the video camera’s cable [Washington Post]. The three-inch crustacean in their video (and pictured in the image here) is a Lyssianasid amphipod, a relative of a shrimp. The team also retrieved what they believe to be a tentacle from a jellyfish.
“We were operating on the presumption that nothing’s there,” said NASA ice scientist Robert Bindschadler, who will be presenting the initial findings and a video at an American Geophysical Union meeting Wednesday. “It was a shrimp you’d enjoy having on your plate” [AP]. Indeed, researchers previously believed that nothing more complex than microbes could live in such a hostile place, beneath an ice sheet in total darkness. While complex organisms have shown up before in retreating glaciers, this seems to be the first time any have been found 600 feet down below an intact sheet of ice.
Water, water everywhere. Another pass of Saturn’s moon Enceladus, made by the Cassini spacecraft last November, shows at least 30 geysers blasting water from the moon’s south pole. That’s 20 more than were previously known at that location. In addition, the most detailed infrared map of one of the south pole’s fissures, where jets emanate, indicates that the surface temperature there might be as high as 200 kelvins (-73º Celsius), or about 20 kelvins warmer than previously estimated [Discovery News]. Cassini drew to within about 1,000 miles of Enceladus to measure this geological feature, which is a fracture–one of the moon’s so-called “tiger stripes”–about a quarter-mile deep officially called Baghdad Sulcus.
While 200 kelvins is still a frigid temperature for we humans, research team member John Spencer said it could make a big difference on Enceladus. “The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground,” Spencer said. ”Results like this make Enceladus one of the most exciting places we’ve found in the solar system” [Wired.com].
Bad Astronomy: Enceladus Is Erupting!
80beats: Cassini Probe Finds “Ingredients For Life” on Saturn’s Moon Enceladus
80beats: Antifreeze Might Allow For Oceans—And Life—On Enceladus
80beats: Does Enceladus, Saturn’s Geyser-Spouting Moon, Have Liquid Oceans?
80beats: New Evidence of Hospitable Conditions for Life on Saturn’s Moons
80beats: Geysers From Saturn’s Moon May Indicate Liquid Lakes, and a Chance for Life
80beats: Cassini Spacecraft Snaps Pictures of Saturn’s Geyser-Spouting Moon
Five years ago, the Cassini spacecraft first detected plumes of water ice emanating from Saturn’s moon Enceladus, making the moon one of the best hopes for finding life somewhere else in the solar system. Astronomers have argued over whether or not those jets come from a subsurface ocean of liquid water, but new findings by Cassini provide evidence that water could indeed be sloshing around beneath the frozen surface of this small moon.
During a 2008 pass through the plumes, the spacecraft found negatively charged water molecules. Back home this short-lived type of ion is produced where water is moving, such as in waterfalls or crashing ocean waves [Scientific American]. Researcher Andrew Coates led the study, which is coming out in the journal Icarus.
What lies beneath the icy crust of Enceladus? Ever since the NASA space probe Cassini snapped pictures of the Saturnian moon expelling enormous jets of icy vapor from fissures near its south pole in 2005, planetary scientists have debated whether the evidence points to liquid oceans beneath the moon’s surface. Now, a new chemical analysis of the plume bolsters the oceanic theory, thanks to the detection of a mundane chemical: ammonia. Says study coauthor Jonathan Lunine: “This is the first time Cassini has actually been able to ’smell’ ammonia…. And because ammonia is an antifreeze, it probably ensures that there is liquid water in the interior of Enceladus.” And where there’s water, there could be life [Wired.com].
Last month, another team of researchers also argued for the presence of an ocean when they published their discovery of sodium salts in Saturn’s outer-most ring which is thought to originate from Enceladus’ plume material. “The two studies are complimentary and now, for the first time, we are getting an idea of the full picture of what’s happening on Enceladus,” [Chemistry World], says Frank Postberg, lead author of that earlier study. However, Postberg’s study was contested by another paper that found no traces of sodium vapor around Enceladus, leaving the debate unresolved. Sodium is thought to be an indicator of liquid water because it suggests that salt leached from rocks into the water.
Saturn’s moon Enceladus got humanity’s attention in 2005 when surprised astronomers detected jets of ice and gas spraying out from the moon’s icy surface, and since then researchers have eagerly investigated the possibility that the jets might emanate from liquid oceans beneath the frozen crust. A moon with liquid water would be of great interest, because it would be more likely to host extraterrestrial microbes. Now, two new studies with somewhat contradictory results have deepened the mystery of what lies beneath Enceladus’s shell of ice.
Both groups of researchers were looking for sodium near Enceladus; one found it, the other didn’t. Sodium is interesting because it indicates that deep under the ice, liquid water has been in contact with rocks, which leach salts [ScienceNOW Daily News]. The dissolved sodium, along with water, would be shot into space in the geysers, and some of the sodium would be trapped in ice crystals as they formed. The first research group found sodium traces in Saturn’s E ring, a wide band of ice particles that is believed to be replenished by Enceladus’s jets. “Those salty grains provide our current best smoking (or steaming) gun pointing to present-day liquid water near the surface of Enceladus” [Wired.com], wrote space scientist John Spencer in an essay accompanying the findings.
Which celestial bodies are more likely to host extraterrestrial life: Saturn’s hazy moon Titan and water-spewing moon Enceladus, or Jupiter’s icy moons Europa and Ganymede, which may have liquid oceans beneath their frozen crusts? That’s the difficult question facing NASA and the European Space Agency (ESA) as they try to decide where to send the next planetary probe. By the end of this month, agency officials plan to pick a destination for a massive mission, costing nearly US$4 billion, to be launched around 2020 for the distant reaches of the Solar System. The battle pits Titan, which recent discoveries have made the cool new kid on the block, against Jupiter’s moon Europa, which has long sat atop community wish lists [Nature News].
In advance of that decision, the space agencies have released details of the dueling proposals. The potential Saturn mission would follow up the remarkable discoveries made by the Nasa/Esa Cassini-Huygens mission which continues to operate at the ringed planet…. Cassini has sent back data that indicates Titan is akin to a primitive – albeit frozen – Earth. It has a thick atmosphere and is rich in organic (carbon-rich) molecules [BBC News]. The plan calls for an orbiter that would release a hot air balloon to drift in Titan’s hazy atmosphere and would drop a lander to the surface, where it could float on one of moon’s lakes of liquid ethane and methane. The orbiter would also dip into the atmosphere of Enceladus, which has fired imaginations with the revelation that it has geysers that spew jets of icy water into space.
The space probe Cassini, our emissary to Saturn and its fascinating satellites, has made several new discoveries that lend further credence to the idea that microbial life could evolve on the icy moon Enceladus or the moon Titan, with its lakes of methane. During a flyby of Enceladus Cassini snapped pictures of the moon’s surface and the cracks in its icy crust from which jets of water vapor routinely burst upward. The new pictures suggest that the cracks form when the crust splits and spreads apart in a way that is similar to the mid-ocean ridges central to the tectonic system on our own planet. On Earth the spreading of the sea floor is driven by molten rock; Nasa scientists speculate that the liquid beneath the south pole of Enceladus may be water. “Bit by bit, we’re accumulating the evidence that there is liquid water on Enceladus” [Telegraph], said Cassini scientist Carolyn Porco.
Enceladus is already known to have some of the fundamental chemistry required to make and sustain life. Liquid water currently is the major missing ingredient. Dr Porco commented: “We first discovered this region in early 2005 and now it’s nearly four years later, so it’s still kind of brand new; but already there are some of us who really want to go back with a spacecraft that focuses on the south pole of Enceladus and investigates whether or not it is a site of either pre-biotic or biotic processes” [BBC News].
When NASA’s Cassini spacecraft swooped past Saturn‘s moon Enceladus last year, it got a close-up view of the water vapor and ice plumes that stream away from the small moon. After analyzing the data, researchers say the evidence suggests that the material in the plumes originates as liquid water trapped beneath the moon’s icy surface, which increases the possibility that microbial, extraterrestrial life could exist in the lakes. “We think liquid water is necessary for life and there is more evidence that there is liquid water there,” said lead researcher Candice Hansen…. Scientists are aware of only three places where liquid water exists near the surface of a planet or other body – Earth, Jupiter’s moon Europa and now Enceladus [Telegraph].
Researchers identified four distinct jets within the plume where the water vapor appears to be traveling faster than 1,300 miles per hour. Such high speeds imply that the jets are fed by pressurised water vapour that shoots through narrow openings – which act like rocket nozzles – in the moon’s icy surface. The simplest way to generate such pressures is by evaporating a reservoir of liquid water that lies close to the moon’s surface [New Scientist], researchers say.