The question that has long been unanswered, did Mars ever contain life? This question came to mind when Steven A. Benner brought up the Meteorite found in the Antarctica changed the way scientists thought about ‘life’ and how it they grew away from the carbon-definition theory and focused on the cell definition-theory. Although I am not going to discuss the definition of ‘life’, I will discuss the different arguments that were brought up during the examinations of that Meteorite and whether or not life was discovered.
The Meteorite, named ALH 84001, was observed by the scientists at the Johnson Space Center. Once ALH 84001 got national attention, scientist became interested in the findings and some started to knock down those results. The Mars Meteorite contained several features that were argued to be evidence of life or not included magnetite, wormlike features, and carbonate globules.
During the examination of the meteorite, a mineral known as magnetite was found in it. This was very exciting for the scientists that were investigating it because this magnetite was chemically pure, which could have been from biology. From the article The Continuing Controversy of the Mars Meteorite, Kathie Thomas-Keprta from the Johnson Space Center stated that, “chemically pure magnetite is known from biology. So-called magnetotactic bacteria create a chain of magnetite grains to help orient themselves in their search for nutrients.”(3). However, critics argue that the magnetite did not necessarily come from biology. Shockwaves have been known to generate these magnetite crystals. It may be more persuasive if those magnetite crystals were found as they were created by bacteria on Earth (2). This could be a pretty big breakthrough if the magnetite was positively from a Martian bacterium.
The next argument that has researchers in disagreement is the wormlike structures that was found in ALH 84001's structure. The scientists that discovered the worm like structures that resembled fossil bacteria that looked similar to the structures found on earth. The largest possible fossil that was discovered was less than one hundredth the diameter of a human hair. This could be more evidence that might suggest that ‘life’ did exist on Mars. However, the critics state that the wormlike features could have been from the coating that was used to prepare the Meteorite for electron microscopy (3). An astrobiologist from the Carnegie Institution for Science in Washington, D.C., Andrew Steele, told the article that, “The questions posed by the team were very difficult to refute”(3). The critiques also argued that the fossil size worm holes were way too small to be considered evidence of life. From Steven Benner it was said that, “The most frequently cited ‘‘too small’’ argument compared the size of the ALH ‘‘cells’’ to the ribosome, the molecular machine used by terran life to make proteins”(Benner). It seems that once the researchers realized that these wormlike features might have been caused by their preparations to the Meteorite, they would need to find more evidence.
A third observation by the researchers was the carbonate globules. These carbonate globules made up of 1 percent of the Meteorite. The scientists concluded that these carbonate globules would have been most likely formed in the presence of water (3). This finding suggests that Mars not only have biology on it, but also had water. Once again, the skeptics denied that these carbonate globules were formed from water. Even though they didn’t explain how, they said that the carbonate globules could have formed without the need of Martian microbes.
It seems that no matter what information is discovered with life outside of Earth, there will always be someone there to critique the findings. The researchers that are trying to find evidence of life on Mars, and in rest of the Universe, need to be sure that that have hard evidence to back up their claims. The biggest evidence that the Johnson Space Center found on the ALH 84001 was the magnetite grains and even that evidence was heavily critiqued by other scientists. We may never know if life ever existed on Mars in our lifetime, but with the technology that exists, we are definitely making progress to that answer.
1) Benner, S. A. (2010). Defing Life. Astrobiology .
This Mars meteorite definitely had some promising signatures for life. However, I do not necessarily blame the skeptics, as claims for life should be handled with scrutiny and diligence. In my opinion, it is better to be critical of signs of life than to falsely claim signs of life have been found without proper evidence. The Mars evidence seems really promising, but we still need more samples and evidence.
The search for life will always be one that is criticized by one or another though Mars if any planet has the highest possibility for life that's easily in reach mainly because Mars use to be so earth like and at one point could have had life so your discussion has a lot of merit. If I could suggest anything maybe bring up the triplet's theory and other research.