The possible discovery of Life on Mars



This is a picture of the meteorite ALH84001.
Click on image for full size version (80K JPG)
Image from: NASA
In July, 1996, it was announced that Dr. David McKay, along with a team of scientists at Johnson Space Center (a division of NASA), had discovered possible fossils of bacteria in an ancient rock from Mars. The rock is actually a meteorite named ALH84001, which was found in the Allen Hills in Antarctica in 1984 after having laid around for 12,000 years. While the announcement garnered much excitement at first, upon further study the claims of Martian fossils turned out to be false. NASA said that after two years of study that "a number of lines of evidence have gone away".

The presence of polycyclic-aromatic-hydrocarbons (PAH's), for instance, were originally seen as a possible byproduct of life, but are now viewed as most probably chemicals found on early Mars. Oddly shaped molecules in the meteorite dubbed "worms" resemble many structures created by completely inorganic processes.

Spheres of carbonate were observed in the meteorite which the scientists in 1996 claimed were the fossilized remains of bacteria. However, they are roughly 1000 times smaller than the smallest bacteria on Earth. Organic compounds were found with the carbonate spheres, but it turned out that the organic compounds became a part of the meteorite after it landed on Earth (scientists believe that there were several episodes of contamination when water seeped into the rock). The carbonate spheres do not contain any carbon 14 (an isotope found on Earth), suggesting that they did not originate on Earth. The organic compounds, on the other hand, do contain carbon 14 and entered the meteorite during an episode of contamination.

The environment of Mars in the past was very different than it is today. Conditions then may have been favorable for the existence of life. Even though the Mars meteorite did not turn out to be proof of life on Mars, it certainly does not rule out the possibility that life may at one time have existed on Mars.


The possible discovery of Life on Mars



This is a picture of the meteorite ALH84001.
Click on image for full size version (80K JPG)
Image from: NASA
In July, 1996, it was announced that Dr. David McKay, along with a team of scientists at Johnson Space Center (a division of NASA), had discovered possible fossils of bacteria in a meteorite named ALH84001 that came from Mars. It was found in the Allen Hills in Antarctica in 1984 after having landed there 12,000 years ago. While many scientists were excited at first, much of the proof offered fell apart. NASA said that after two years of study "a number of lines of evidence have gone away".

Several different chemicals and molecular structures were exciting because they looked similar to byproducts of life on Earth. However, these chemicals and structures can also be created without life. Some are even present in deep space on comets, and scientists do not think that they came from Martian life anymore.

Small spheres were observed in the meteorite which the scientists in 1996 claimed were the fossilized remains of bacteria. However, they are roughly 1000 times smaller than the smallest bacteria on Earth, so don't resemble any life thought to be possible. Organic (carbon containing) compounds were found with the spheres, but it turned out that the organic compounds became a part of the meteorite after it landed on Earth (possibly when water seeped in a couple times over the 12,000 years the rock laid in Antarctica). Carbon 14, an isotope found on Earth is present in the organic compounds, but not in the spheres.

The environment of Mars in the past was very different than it is today. Conditions then may have been favorable for the existence of life. Even though the Mars meteorite does not prove life once existed on Mars, it certainly does not disprove the possibility.


The possible discovery of Life on Mars



This is a picture of the meteorite ALH84001.
Click on image for full size version (80K JPG)
Image from: NASA
In July, 1996 a team of scientists said that they had discovered possible fossils of bacteria in a meteorite named ALH84001 that came from Mars. It was found in Antarctica in 1984 after having landed there 12,000 years ago. After a couple years of study, it appears that the scientists were wrong.

Some chemicals found in the meteorite look like chemicals created by life on Earth. These same chemicals can also be created without the help of life. Small balls or spheres were seen in the meteorite which the scientists in 1996 thought were the fossilized remains of bacteria. However, they are roughly 1000 times smaller than the smallest life known on Earth. This seems much too small to be life. Other pieces of evidence turned out to have come from Earth after the rock landed here, and not from Mars at all.

The environment of Mars in the past was very different than it is today. Conditions then may have been favorable for the existence of life. Its too bad, but the Mars meteorite just isn't the proof that some people hoped it would be.




Last modified March 24, 1997 by the Windows Team

The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). ©1995-1999, 2000 The Regents of the University of Michigan; ©2000-05 University Corporation for Atmospheric Research. All Rights Reserved. Site policies and disclaimer