A Martian Christmas Gift?
Published on Dec 5, 2006 at 12:22 am.
2 Comments.
Filed under Mars, amusement, astrobiology.
Are you looking for that perfect Christmas gift for an astronomer? Here’s a nice little stocking stuffer. It is a Mars microbe (sort of). Actually, it is a little stuffed toy made to look like one interpretation of Mars life. It is from a company called Giant Microbes that sells all sorts of bacteria and virus dolls (and some insects, too). Hmm. This could be stocking stuffers for all your scientist friends. I have one, and it is just too cute.
Now, let me point out that this probably isn’t what Mars life looked like, but it is a good item to start a conversation about Mars life with. Ever since observations in the 19th Century showed some similarities between Earth and Mars, there has been speculation that Mars may either harbor life, or may have at one time hosted life. But, speculation as to what that life may have been like has ranged from mundane to wild. Let me give you some background on why this company even has a Mars life doll that looks like this.
The story goes back several billion years. At that time, Mars was quite different from the way that it is today. The atmosphere was thicker, and liquid water was present. Some of the ingredients were there for life. Mars was also more volcanically active then, with new rocks being formed all the time. But, the atmosphere became thinner and there is now no longer liquid water at the planet’s surface. Then, not much happened in our story until about 16 million years ago. A comet or asteroid slammed into Mars. The resulting explosion excavated a crater. Some of the material forming the surface layers of Mars was ejected at very high velocity into space. In fact, some of these rocks were moving in excess of the Martian escape velocity. So, those rocks flew out into space, and began orbiting the Sun. Eventually, one of those rocks encountered Earth. That rock blazed through the atmosphere as a meteor, and it even survived passage through the atmosphere to fall to the ground as a meteorite about 13,000 years ago, landing in Antarctica. It was found by an expedition looking for meteorites in 1984. This rock was the first meteorite collected in 1984 in the Allan Hills region, so it was designated ALH 84001.
Now, none of these things is really so unusual. In fact, we’ve found 57 Martian meteorites laying around Earth. ALH84001 was just another one. Actually, for nearly a decade, no one had looked at it very closely because it had been misclassified as another type of meteorite. Eventually, the mistake was rectified in the mid 1990’s, and a team of researchers at NASA’s Johnson Space Center realized that they had a rare piece of Mars to study (at that time, only 12 Martian meteorites had been found). So, working with researchers from Stanford University, they began to study it.
Studies of ALH84001 showed the presence of amino acids and polycyclic aromatic hydrocarbons (PAHs). This was exciting because the Viking landers twenty years earlier had failed to find organic molecules in Martian soil. Organic molecules are carbon containing molecules, and carbon is believed to be essential to life. The presence of these chemicals in the Martian rock, though, do not mean that life must have been there. Similar findings have been made in meteorites that no one believes ever had life. But, the most thought provoking discovery was of small carbonate features that looked almost like eggs or worms. Near these features were found iron sulfides and magnetite, both of which are sometimes produced by Earth bacteria. The researchers quickly concluded that they may have found fossilized lifeforms. Their announcement made quite a stir, and was the source of so much press attention that in early August, 1996, President Bill Clinton made a special televised statement to the press regarding the possible discovery of life on Mars.
I watched that press conference, and was amazed by the photos of the “Mars life” that they showed. I was even interviewed by one of the local TV stations for my take on the story. Well, I don’t think that they liked what I had to say, because they quickly ran off to interview other people at one of the planetariums in the area that were going on about how spectacular a find that this was. I had told them that this is a rather amazing claim, and that it needed to be backed up by amazing evidence, not just intereting looking photos. I also pointed out that announcing a scientific find to the press before it has been considered by one’s peers is poor practice, and that this work had not even been published yet, so no one has had a chance to go over it to see if they were jumping to conclusions or if they had a valid point. I also said that one rock, with a few intesting features, won’t really be enough to say one way or another. More data are needed. Anyway, that was nowhere near as exciting as interviewing people who had little science training and were taking these announcements as ironclad fact. It was several years before they interviewed me again for anything!
Interestingly, once other researchers got a chance to look at the findings, the excitement faded. It seems that these “critters” are too small. Biologists tell me that they are even smaller than nanobacteria, and that they are smaller than many viruses. That makes them far too small to be cellular in nature, and if they are not cellular, then they can not produce the sort of features that the researchers were claiming. Geologists then started looking at the findings and they claim that every one of the findings could be explained by various geological processes, without life being involved. Though the jury remains out, the vast majority of scientists (other than the researches who made the initial announcent) feel that calling these findings life is jumping the gun. Most feel that these interesting little features are not fossilized lifeforms.
But, even if these things are not fossilized life, they did spur a lot of interest in Mars and the conditions necessary for life on Mars. So, as often happens in science, a negative finding turns out to be useful. But, the team of researchers is still pretty insistent that these features are biologic in origin. As I told the news crew, though, one rock isn’t really enough to say for sure. My feeling is that these are not fossilized life. But, even so, I really like my stuffed Martian!
-Astroprof
Darnell Clayton on December 5, 2006 at 3:42 pm: 1
Although pretty interesting, unless they can find something on Mars alive, then there might be no evidence that their is life on that sterile planet (unless of course we design something that can survive there).
Astroprof on December 5, 2006 at 10:03 pm: 2
I totally agree. I don’t think that these features are any indication of life, fossilized or not. And, even if it turns out to really be fossilized life, then that does not mean that there is life on Mars currently.