Bakersfield Night Sky – December 1, 2012
By Nick Strobel
There certainly has been a bit of buzz on the internet about a major discovery by the Curiosity rover on Mars all based on a cryptic statement from the lead scientist, John Grotzinger, that the data returned from one of the instruments on the rover called "Sample Analysis at Mars" ( "SAM" for short) are going to be "one for the history books." The comment was made to a reporter from National Public Radio during a visit to Grotzinger's office. Grotzinger was looking at the data on his computer screen while the reporter was setting up his equipment for the interview when he made the comment. After he made that innocent comment, Grotzinger wouldn't say anything more about the discovery for a couple of reasons. The first reason is that the results from SAM must be double-checked many times to rule out less exciting explanations for the results (extraordinary claims require extraordinary evidence). That multiple double-checking had not been done yet when Grotzinger was interviewed. The second reason is that the media likes to hype or exaggerate discoveries in order to attract viewers or listeners and NASA has played into that at times. Grotzinger may have regretted making that comment right after he made it realizing that what he takes to be an earthshaking (mars-shaking?) discovery and what the general public, brought up on whiz-bang science fiction movies, takes to be an earthshaking discovery are often two different things and that he had better not say anything more before he got into more trouble. He probably wondered if he just started an internet frenzy. Judging by the news reports after the NPR report was broadcast and the hyper-amplification happening because of social media, I would say he has. The Curiosity twitter feed just before Thanksgiving said that its discovery on Mars was "that rumors spread fast online."
The NPR story included a humorous story about the difference between a scientist's excitement of his or her work and the general public's perception of it. A scientist from the team that made the well-publicized announcement in 1996 of possible fossils of microbial martian life in a meteorite from Mars described what happened when he shared his discovery with his family before the announcement. Richard Zare burst the news to his family at dinner. His daughter looked at him (probably with the same uninterested expression my teenage+tween daughters give me all the time when I talk about my work) and asked him to pass the ketchup. Sigh! The features in the meteorite taken to be martian fossil microbes turned out later to be inconclusive since other science teams figured out less exciting, non-biological ways that those features could be made. With regard to Curiosity's discovery, we'll have to wait until Monday, December 3rd, for the announcement to be made at the meeting of the American Geophysical Union.
I'm in the dark on what the discovery is. No, I don't have an inside scoop on what it is, but I'm going to throw caution to the wind and speculate two days before the official announcement. I'm guessing that Curiosity has found organic molecules on the surface of Mars. Organic molecules, based on the element carbon, are the building block ingredients needed for life. Now, organic molecules are found all over the place in the solar system, including in carbonaceous meteorites falling to Earth all the time, and beyond. The reason why finding organic molecules on Mars would be such an important result is that the gas chromatograph/mass spectrometer instrument on the Viking lander mission in 1976 had definitively ruled out the presence of organic molecules in the martian soil. The soil appeared to be sterile and so chemically reactive that microbes would be quickly destroyed in the soil. That negative result overrode another Viking experiment called the "Labeled Release Experiment" that seemed to show signs of metabolism. In that experiment, some "goop" (nutrients) that had been radioactively tagged with C-14 and S-35 were mixed with the soil to see if any microbes would metabolize the nutrients and release gas with the radioactive tags. The gas was released as expected from biological activity and the activity dropped off as the soil was heated up eventually to 160º C. Two other experiments on Viking initially found hints of biological activity but further testing of their samples found that the reactions could happen via some sort of martian geochemical process. The Labeled Release Experiment, though, could not be explained away so easily. At least not until the gas chromatograph/mass spectrometer instrument seemed to show that there were no organic molecules present at all. The Viking science team was forced to conclude that some sort of strange chemistry was going on that mimicked metabolism on Mars.
Over thirty years later the Mars Phoenix mission found perchlorate in the soil at its location in arctic region of Mars. If perchlorate is found at the Viking lander locations on Mars, the perchlorate in the soil would have broken down any organic compounds that would have been in the soil when the soil was heated up during the Viking mass spec test for organics. Although perchlorate is toxic to most Earth life, it can be food for some types of microbes. Water vapor from the atmosphere could attach to the perchlorate to form a thin film layer of water for biological activity. In addition, perchlorate in water can lower its freezing temperature enough to keep water liquid even in Mars' cold temperatures. So, if organic molecules have been found by Curiosity, then the Labeled Release Experiment's results from Viking cannot be dismissed. While Curiosity doesn't have the instruments to test for biological activity, SAM does have the capability to determine the ratios of Carbon-12 to Carbon-13 isotopes in the soil. The Carbon-13 isotope has one extra neutron in its nucleus, making it a little bit more massive than Carbon-12. Life on Earth prefers to use organic molecules with Carbon-12 over those with Carbon-13, so residues from terrestrial biology are enhanced with Carbon-12 compared to non-biological carbonates such as limestone. Enhanced amounts of Carbon-12 relative to Carbon-13 have been used to argue for some extremely old residues of carbon as evidence for ancient life beginning on Earth as far back as 3.8 billion years ago (other more conclusive evidence shows that life on Earth definitely began at least 3.5 billion years ago). I do not think that the Curiosity science team will have anything to say about carbon isotope ratios, though. Just finding organic molecules would be a big enough deal as it is. However, remember that I'm speculating on what is Curiosity's major discovery. (Whether this fans the flames or dampens them probably depends on the reader.)
Update: A NASA news release today (Nov 29th) blew all of my speculation above out of the water. No organics were found. Here's a brief version of the release:
PASADENA, Calif. -- The next news conference about the NASA Mars rover Curiosity will be held at 9 a.m. Monday, Dec. 3, in San Francisco at the Fall Meeting of the American Geophysical Union (AGU).
Rumors and speculation that there are major new findings from the mission at this early stage are incorrect. The news conference will be an update about first use of the rover's full array of analytical instruments to investigate a drift of sandy soil. One class of substances Curiosity is checking for is organic compounds -- carbon-containing chemicals that can be ingredients for life. At this point in the mission, the instruments on the rover have not detected any definitive evidence of Martian organics.
The Mars Science Laboratory Project and its Curiosity rover are less than four months into a two-year prime mission to investigate whether conditions in Mars' Gale Crater may have been favorable for microbial life. Curiosity is exceeding all expectations for a new mission with all of the instruments and measurement systems performing well. This is spectacular for such a complex system, and one that is operated so far away on Mars by people here on planet Earth. The mission already has found an ancient riverbed on the Red Planet, and there is every expectation for remarkable discoveries still to come.
The view of Mars from Earth is not so exciting. Mars appears low in the southwestern sky in the twilight glow of sunset just about a fist-width at arm's length above a flat horizon. It is dim enough that you'll probably need binoculars to spot it—use the third chart below to help you locate it. It will be above the handle part of the Teapot of Sagittarius. Jupiter will already be up in the east at sunset. The first chart below shows the view at 10 PM when Jupiter will be two-thirds of the way up in the eastern sky. It will be just above one edge of Taurus' head and still blazing as it continues moving retrograde. The Waning Gibbous Moon will rise a little after 8 PM next to the stars of Gemini. By 10 PM, the stars of Orion and his two hunting dogs, Canis Major and Canis Minor, will be easily visible in the eastern sky as shown in the attached chart. The three belt stars of Orion will point down to bright Sirius at the nose of Canis Major that will try to compete with Jupiter in brightness. Jupiter will be officially at opposition tomorrow, meaning that it will be directly opposite the Sun on our sky and get up highest due south at midnight.
Venus has now passed by Saturn from their very close conjunction in the early morning sky last Monday. Venus is situated halfway between Saturn on the eastern end of Virgo and Mercury in the middle of Libra (see the second chart below). Saturn will be visible in the east by around 4:30 AM, Venus by around 5 AM, and Mercury by around 5:30 AM. The Waning Crescent Moon will pass by Saturn on December 10th and then by Venus the following morning.
The Geminid meteor shower will peak on the night of December 13/14. On that night the Moon will be just barely past new phase, so there will be no moonlight to wash out the view. The Geminid meteor shower happens every year at this time when the Earth runs into the dust trail left behind by the asteroid 3200 Phaethon that is probably actually a "dead" comet that has lost all of its volatile materials from repeated passages around the Sun. The dust grains in the Geminids hit the Earth's atmosphere at about 22 miles per second. The meteors will appear to streak out of a point next to Castor at the top end of Gemini (see the first chart below). The Geminids usually put on a good show every year with up to about 120 meteors visible per hour to those under a nice dark sky away from the city lights. With no Moon to spoil the view this year, the show should be especially good.
After the December 6th showing of "Season of Light", the William M Thomas Planetarium will close for Bakersfield College's winter break.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com