Meteorite Helps Build the Case for Ancient Life on Mars

Yamato 000593
Credit: JPL

For those who remember, the discovery of possible signs of ancient microbial life on Martian meteorite ALH 84001 sparked enormous debate in 1996,  temporarily convincing a great many people that we had at last found conclusive evidence of life on Mars.

As the years rolled on, alternate explanations appeared to answer the questions raised by the team of David McKay, Everett Gibson and Kathie Thomas-Keprta.  Throughout it all, the team remained resolute. It appears to be paying off.

NASA’s Jet Propulsion Laboratory announced today the results of an investigation by members of the same team into another meteorite, Yamato 000593, and while not absolutely conclusive, they clearly help to build the case that Mars once harbored simple forms of life.

According to the release:

“The rock was found on the Yamato Glacier in Antarctica by the Japanese Antarctic Research Expedition in 2000. The meteorite was classified as a nakhlite, a subgroup of Martian meteorites. Martian meteoritic material is distinguished from other meteorites and materials from Earth and the moon by the composition of the oxygen atoms within the silicate minerals and trapped Martian atmospheric gases.

The team found two distinctive sets of features associated with Martian-derived clay. They found tunnel and micro-tunnel structures that thread their way throughout Yamato 000593. The observed micro-tunnels display curved, undulating shapes consistent with bio-alteration textures observed in terrestrial basaltic glasses, previously reported by researchers who study interactions of bacteria with basaltic materials on Earth.

The second set of features consists of nanometer- to-micrometer-sized spherules that are sandwiched between layers within the rock and are distinct from carbonate and the underlying silicate layer. Similar spherical features have been previously seen in the Martian meteorite Nakhla that fell in 1911 in Egypt. Composition measurements of the Y000593 spherules show that they are significantly enriched in carbon compared to the nearby surrounding iddingsite layers.

A striking observation is that these two sets of features in Y000593, recovered from Antarctica after about 50,000 years residence time, are similar to features found in Nakhla, an observed fall collected shortly after landing.”

The full release is here, and it is definitely worth a read.

Note: Unless a new meteorite happens to fall out of the sky and come crashing through the roof into a sterile lab, it is always going to be possible to challenge meteorite based evidence on the grounds that it could be contaminated by life on Earth. There are two steps to resolving this debate. The first is a Mars Sample Return Mission, and the second is to go there and see for ourselves.