Is there a methane habitable zone?

A sunlight glint off a methane lake near Titan’s north pole (infrared image). Credit: NASA/JPL/University of Arizona/DLR

For a long time now, we have heard the mantra “follow the water” when it comes to searching for life elsewhere. Life as we know it here on Earth requires liquid water, whether it is tiny microbes or elephants. It has thus been assumed that carbon-based life somewhere else that is basically similar to ours in its chemical makeup (another assumption) would also require water for its survival and growth. But is that necessarily true? In recent years, more consideration has been given to the possibility that life could develop in other mediums as well, besides water. A liquid is still ideal, for allowing the necessary molecules to bond together. So what are the alternatives? Well, one of the most interesting possibilities is something we have already seen now elsewhere in our solar system – liquid methane…

See Universe Today for the full article.

Poll: which Discovery mission would you vote for?

As a follow-on to the previous post, which newly proposed mission for NASA’s Discovery program would you like to see happen? Only one will be selected next year, to launch in 2016…

Sailing the seas of Titan

It was announced last week that there are three final mission proposals for NASA’s Discovery program, with one of them to be selected in 2012, for development and launch in 2016.

The first is the Geophysical Monitoring Station (GEMS) which would study the interior structure and composition of Mars. The second is the Titan Mare Explorer (TiME), which would land in and float on one the many methane lakes and seas on Titan. The third, Comet Hopper, would land on the same comet multiple times to observe changes over time.

Credit: NASA/JPL

There has been a lot of discussion about this, with most people opting for the Titan mission. And that would be my choice as well, since we’ve already been to Mars many times now (and more missions going there soon) and have observed numerous comets up close already by various spacecraft. But the chance to actually sail a boat as such on an alien sea, can we really pass that up? So far, Titan is the only other place known to have extensive rivers, lakes and seas on its surface. While being a much colder environment than anywhere on earth, some scientists have postulated the possibilty of some form of life there. Let’s go look…!

Miscellaneous wrap-up

As noted earlier, I missed posting more the last few weeks due to being sick, but here is a condensed summary of some of the other recent interesting updates as we come to the end of 2010…

Does Pluto, of all places, have a subsurface ocean? This new report says maybe; Cassini has found new evidence for an ice volcano on Titan; the building blocks of life could possibly form on Titan’s surface more easily than thought if there is any liquid water temporarily on the surface from ice volcano eruptions (or comet impacts); there’s a new theory on how Iapetus may have obtained its odd equatorial ridge; the “arsenic life” discovery continues to be criticized by some other scientists (see also here) while the scientists involved have responded and rebutted those claims (see also here); the Spitzer space telescope has found the first known carbon-rich exoplanet; a fourth large exoplanet has been photographed orbiting a star 129 light-years from Earth; another smaller exoplanet, a “super-Earth” was found to have an atmosphere with either high clouds or hot steam; a new study says that the entire Tharsis Rise on Mars should be named the largest known volcano in the solar system instead of the current Olympus Mons (one of four volcanoes that are part of Tharsis Rise); the warm fissures on Enceladus, the source of its water-ice geysers, were seen up-close by Cassini again; there may be another Jupiter-sized planet hiding out in the outer solar system; and finally, the current known exoplanet count is now 516 (and the hope was for at least 500 by the end of this month)!

Highlighted by, among other things, the next exoplanet update from Kepler in February and the launch of Curiosity, the next bigger and better Mars rover, in November, 2011 should also be an interesting year…

Astrobiology news conference follow-up

Credit: Science/AAAS

The much-anticipated NASA news conference is now over, so what was revealed, exactly? Not alien life (yet), but still an astrobiology-related finding on Earth that will greatly affect the search, just as the initial NASA press release stated. There was, again, a lot of overblown speculation, mostly on the part of various media and bloggers, that such life itself had been confirmed finally, although this was not based on the known facts at the time.

As most serious researchers, bloggers, etc. had surmised, it was a more down-to-earth discovery, but still indeed significant. The consensus that it had to do with a possible shadow biosphere, as mentioned in my previous post, was not too far off. The discovery involves bacteria that can substitute arsenic (usually extremely toxic) for phosphorus, one of the six elements normally found in all known life (on Earth anyway); the others being carbon, hydrogen, nitrogen, oxygen and sulfur. The six building blocks of life as we know it. Or perhaps knew it, now.

Credit: Science/AAAS

The bacteria, GFAJ-1, found in arsenic-rich Mono Lake, California, are the first to be observed doing this. The key is that the bacteria apparently don’t just tolerate the arsenic as other organisms can do, but they seem to actually incorporate it into their DNA and cellular structure in place of the phosphorus. The studies are still on-going, and there is the usual, but necessary, skepticism from others in the scientific community, but if the results are confirmed by others, it will redefine what forms life can take, and increase the variety of environments where such life could exist outside of Earth, such as Titan (whose cold but wet methane environment would be more suited for arsenic-based life according to some recent studies), Mars, Enceladus, etc.

Some scientists are arguing that this has more to do with adaptation than a unique form of evolution, hence not a true shadow biosphere or “second genesis” (truly unique life which arose completely independently of all other known life on Earth). Even if so, it is still yet another example of the increasingly wide types of environments life can be found in, notably those long thought to be too toxic. And from that we can only learn more.

Additional good coverage of the news conference is here, here, here, here and here.

NASA news conference on astrobiology discovery (updated)

Now this sounds interesting… NASA will hold a news conference on December 2 at 11:00 am PT (2:00 pm ET) to discuss an “astrobiology discovery” that will “impact the search for evidence of extraterrestrial life.” Details are embargoed until the time of the conference, so what this entails exactly isn’t known yet. It will be held at NASA headquarters in Washington, broadcast live on NASA Television and streamed on the NASA website. Let the speculation begin…

Addendum (November 30):

From the discussions going on, it appears that the news conference probably has something to do with shadow biospheres, the search for truly alien forms of primitive life that co-exist with us here on Earth but based on biochemistry different from all other known life forms, specifically arsenic instead of phosphorous, for example. Such confirmation would make the search for extraterrestrial “life as we don’t know it” much more plausible and perhaps easier to find. From this update:

“Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere.”

“All known life requires phosphorus (P) in the form of inorganic phosphate (PO43- or Pi) and phosphate-containing organic molecules. Piserves as the backbone of the nucleic acids that constitute genetic material and as the major repository of chemical energy for metabolism in polyphosphate bonds. Arsenic (As) lies directly below P on the periodic table and so the two elements share many chemical properties, although their chemistries are sufficiently dissimilar that As cannot directly replace P in modern biochemistry. Arsenic is toxic because As and P are similar enough that organisms attempt this substitution. We hypothesize that ancient biochemical systems, analogous to but distinct from those known today, could have utilized arsenate in the equivalent biological role as phosphate. Organisms utilizing such ‘weird life’ biochemical pathways may have supported a ‘shadow biosphere’ at the time of the origin and early evolution of life on Earth or on other planets. Such organisms may even persist on Earth today, undetected, in unusual niches.”

Some of the listed speakers have been involved in this kind of research, including how it may apply to exotic environments such as on Titan (possible methane-based life, as discussed previously) as well as Mars, etc. See also this update today here. Is this what will be announced? We’ll see Thursday, but it would seem to fit with the speakers’ backgrounds as well as the description given, of a discovery that will impact the search for extraterrestrial life. There has been a lot of speculation today that some kind of such life has already been found in one of these places, but that would appear to be very premature, given a look at the actual available information, in context.


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