by Paul Gilster | Feb 28, 2005 | Astrobiology and SETI
Here’s an image of the possible Martian pack ice, taken by Mars Express’ High Resolution Stereo Camera (HRSC), which is imaging the entire planet in full colour, 3-D and with a resolution of about 10 metres. The 3-D capability allows us to see Martian topography in unprecedented detail. Look here for other extraordinarily detailed images.
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, during orbit 32, shows what appears to be a dust-covered frozen sea near the Martian equator. It shows a flat plain, part of the Elysium Planitia. The scene is a few tens of kilometres across, centred on latitude 5º North and longitude 150º East. Credits: ESA/DLR/FU Berlin (G. Neukum)
Meanwhile, findings from Mars Express were discussed in a news conference on the 25th. To say the session was packed with news is an understatement: we have not only the possible pack ice but discussions of Martian methane and formaledhyde and their significance for the hunt for life, as well as much on volcanic and geological activity (some of it evidently recent, according to ESA). The six instruments on Mars Express have had quite a year. You can read more on what each has discovered in this ESA press release.
Also announced at the session were the results of a poll of many of the 250 Mars experts present. 75 percent of them said no when asked whether life could be present on Mars today, though when asked whether life might once have existed on the Red Planet, 75 percent said yes. The above image — and the presence of methane in the atmosphere — remain provocative. Surely the demand for a sample return mission will continue to grow.
by Paul Gilster | Feb 28, 2005 | Deep Sky Astronomy & Telescopes, Exoplanetary Science
The American Astronomical Society meeting in San Diego yielded results we’ll be discussing all year. One study that comes immediately to mind (with a paper scheduled for the Astronomical Journal in April) is the work of Wei-Chun Jao and the Research Consortium on Nearby Stars (RECONS) team at Georgia State University, who have measured the distance to four stars — all of them red dwarfs — within 33 light years of the Sun. All told, the team has found 26 new neighbors within 25 parsecs (82 light-years), along with the first confirmed binaries comprising a red subdwarf and a white dwarf.
Subdwarfs are highly unusual stars, with extremely low metallicity; i.e., few elements heavier than hydrogen and helium. From a press release on the star measurements:
Another indicator that both systems are old is that each travels through the Galaxy at nearly 150 km/sec (roughly 100 miles/sec). Contrary to people, older stars like the Jupiter-sized red subdwarfs generally move faster than their younger counterparts that are still hanging around their stellar nurseries, and the two discovered systems are moving about three times faster than even middle aged stars. “It’s amazing to see two senior citizens rushing through our neighborhood'”, says Jao, “and they are carrying extremely dense baggages with them.” The white dwarf companions are small objects the size of the Earth that contain roughly half the mass of our Sun, but they are unable to burn any elemental fuel in internal reactions, so they cool down as time passes. Consequently, the two galactic fossils discovered provide a new laboratory that can be used by astronomers to understand the cooling character of white dwarfs, and to probe the earliest moments of our Galaxy’s life.
What’s going on in this work is that we now have better tools to study stars with high proper motion (more than 1 arcsecond each year). These stars are all nearby, but they have been overlooked because they are small and emit little light. And while we presently know of fewer than 3000 stars within eighty light years, some astronomers estimate that there should be 10,000 within that region of space. Finding them is important as we move toward developing the Terrestrial Planet Finder mission, the NASA spacecraft that will look for Earth-like planets. In many ways, projects like RECONS are hunting for targets that may one day be visited by our robotic probes.
One star the team worked on, DENIS 1048-3956, is only 13 light-years away and thus ranks as the 28th nearest stellar system. Some data on the star (drawn from Ken Croswell’s Pinpointing a Stellar Neighbor): “The star emits only 0.00015 percent as much visible light as the Sun and, therefore, requires 1,800 years to generate the same amount of light the Sun throws off in a 24-hour day. If the star took the Sun’s place, it would look dimmer than the Full Moon.” DENIS 1048-3956 is either a red or a brown dwarf, and a known emitter of radio flares that may be a consequence of its rapid rotation.
A map of the Sun’s 25 nearest neighbors is available in Nearest 25 Star Systems at the RECONS site. Among other good things at the site is a list of the One Hundred Nearest Star Systems and links to the Nearby Stars Database, which is based on the NStars project at Northern Arizona University.
The upcoming paper is Wei Chun-Jao, Todd Henry, et al.,”The Solar Neighborhood XIII: Parallax Results from the CTIOPI 0.9-m Program — Stars with mu >= 1″/year (MOTION Sample),” which can be seen in preprint form at the ArXiv site. RECONS works with data from the 0.9m (36in) telescope at the Cerro Tololo Interamerican Observatory in Chile.
by Paul Gilster | Feb 26, 2005 | Outer Solar System
Twenty-four craters on Saturn’s tiny moon Phoebe have now been deemed prominent enough to receive their own names. Phoebe was honored by the names of the Argonauts, the explorers who sailed with Jason to find the golden fleece; its largest crater has been christened Jason. The tale was known in the days of Homer and may have served as a pattern for the wanderings of Odysseus. It is most famously told in a four-book epic by Apollonius of Rhodes, one time custodian of the fabulous library of Alexandria.
“We picked the legend of the Argonauts for Phoebe as it has some resonance with the exploration of the Saturn system by Cassini-Huygens,” said Dr. Toby Owen, of the University of Hawaii at Manoa. He is the chairman of the International Astronomical Union Outer Solar System Task Group and an interdisciplinary scientist on the Cassini-Huygens mission. “We can’t say that our participating scientists include heroes like Hercules and Atalanta, but they do represent a wide, international spectrum of outstanding people who were willing to take the risk of joining this voyage to a distant realm in hopes of bringing back a grand prize”.
Thus the wonderful practice of astronomical naming continues (and think what a strain we’ll place on it when we get enough data to start naming all the exoplanets, and one day, surface features on them as well!) The naming of names (and yes, I’m deliberately invoking the Ray Bradbury story of the same name) is done through cooperation between the International Astronomical Union, the U.S. Geological Survey, and NASA. See the Gazetteer of Planetary Nomenclature for a database of planetary feature names. And you can read “The Naming of Names” in The Martian Chronicles, which has much to say about how names link people to places and gradually change them.
Image credit: NASA/JPL/Space Science Institute
Of course, astronomical naming has to be practical as well as mythological. Thus names are chosen according to the legends surrounding the name of the object itself; when names run out, additional creativity is demanded. The result is a wonderful melange of ancient legends in often fascinating new combinations. Phoebe herself was a Titan, the daughter of Uranus and Gaea.
As for the satellite Phoebe, it is a small object (about 220 kilometers across), but now a more familiar one. “With the assignment of names to craters on its surface, Phoebe now joins the ranks of charted worlds” said Dr. Torrence Johnson, Cassini imaging team member at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., who coordinated the naming of the Phoebe craters with the IAU.
by Paul Gilster | Feb 25, 2005 | Astrobiology and SETI
Storing and preserving living cells at low temperatures is a staple of science fiction. Who knows how many fictional interstellar journeys have taken place with the crew in cryogenic suspension (my favorite, Van Vogt’s “Far Centaurus,” springs quickly to mind, but there are many possible references). And with the possibility of Martian ice — even an ancient Martian sea — under observation by Mars Express, the question of life surviving in extreme conditions is drawing increased attention.
Which is why the discovery of of a new bacterium called Carnobacterium pleistocenium is so interesting. NASA astrobiologist Richard Hoover and his team found the anaerobic bacteria, which grow on sugars and proteins in the absence of oxygen, at the U.S. Army’s Cold Regions Research and Engineering Laboratory tunnel north of Fairbanks, Alaska. The tunnel was created in the 1960s to allow scientists to study permafrost as part of the preparation for building the Trans-Alaska Oil Pipeline.
Hoover’s bacteria not only survive at low temperatures, but can be frozen for long periods before being revived. The bacteria in the team’s samples had actually frozen near the end of the Pleistocene Age, making them tens of thousands of years old. The implications for life in other extreme environments are intriguing, to say the least.
Image: Seen under a microscope, a new bacterium identified by NASA astrobiologist Dr. Richard Hoover and his colleagues thrives — despite having been thawed from ice dating back some 32,000 years, to the Pleistocene era. Living bacteria are stained green. Hoover found the specimens in permafrost deep in the U.S. Army’s Cold Regions Research and Engineering Laboratory near Fox, Alaska. The bacterium — identified over a period of years and published in January 2005 — is a never-before-seen “extremophile,” an organism that lives and thrives in conditions inhospitable to most life on Earth. NASA studies extremophiles to gain insight into the possibilities for life across the cosmos. (Photo courtesy of Asim Bej, University of Alabama at Birmingham)
“Astrobiologists ask, ‘Is life strictly terrestrial in origin, or is it a cosmic imperative, an undeniable, universal biological truth?’ That possibility is central to our desire to explore the universe,” Hoover said. “The existence of microorganisms in these harsh environments suggests — but does not promise — that we might one day discover similar life forms in the glaciers or permafrost of Mars or in the ice crust and oceans of Jupiter’s moon Europa.”
And as for the possible medical uses of this bacterium, Hoover has this to say:
“The enzymes and proteins it possesses, which give it the ability to spring to life after such long periods of dormancy, might hold the key to long-term, cryogenic — or very low temperature — storage of living cells, tissues and perhaps even complex life forms,” Hoover said.
Hoover and collaborators published their work as “Carnobacterium pleistocenium sp. nov., a novel psychrotolerant, facultative anaerobe isolated from permafrost of the Fox Tunnel in Alaska,” which ran in the January 2005 issue of the International Journal of Systematic and Evolutionary Microbiology (Vol. 55, pp. 473-478). You can read a NASA press release on their work here.
by Paul Gilster | Feb 25, 2005 | Astrobiology and SETI
Oliver Morton’s excellent MainlyMartian weblog has a cautionary analysis of Vittorio Formisano’s work on Martian formaldehyde, which we looked at on the 18th. From the weblog:
I’ve posted on the formaldehyde story before. And, even more now than then, I think Formisano is making a mistake…[S]o do a number (quite possibly, from what I hear, all) of his colleagues on the PFS, including those who have more experience modelling atmospheric chemistry and interpreting spectrometer data than Formisano has. I don’t want to rehash everything in the earlier post on the subject, but the gist is that a) formaldehyde is expected to have a very short lifetime in the atmosphere, and thus it is very hard to explain how there could be so much of it and b) earth-based telescopes have looked for the stuff and found no evidence for it even at levels far lower than those that Formisano appears to see.
You can read Morton’s comments here. He has also written thoughtfully on the ‘Elysium Sea’ (the possible Martian pack ice in the Cerberus Fossae region). MainlyMartian is highly recommended reading.
Also, the Australian Broadcasting Company offers a story on Formisano’s work here (thanks to Larry Klaes for the pointer). Quoting Australian geologist Marion Anderson:
While few scientists before today will have seen Formisano’s full data, much of the concern so far has been over the ability of the instrument he is using to specifically pick up the presence of formaldehyde’s absorption spectra.
“They occur at exactly the same wavelength as a number of other very common gases on Mars so a lot of people aren’t 100% sure that what he’s found is formaldehyde,” says Anderson. “It’s literally reading between the lines, in some cases.”