Life in Mars?

ALH84001 slice
ALH84001 (slice)

Nodules
Carbonate nodule

Nodules
Carbonate nodule (slice)

Fossil
Microfossil?

 In the 16 August issue of Science, David McKay et al. report the first identification of organic compounds in a martian meteorite. The authors further suggest that these compounds, in conjunction with a number of other mineralogical features observed in the rock, may be evidence of ancient martian microorganisms:
  • It contains organic molecules (PAH) thay could come from the activity of bacteria or other living organisms, or their degradation (fossilization).
  • It contains carbonate nodules formed within the rock fissures, about 3.6 billion years ago, and are younger than the rock itself.
    • The magnetite and iron-sulfide particles inside the carbonate globules are chemically, structurally and morphologically similar to magnetosome particles produced by bacteria on Earth. On Earth, such closely associated mineralogical features involving both oxidation and reduction are characteristic of biological activity.
    • High-resolution scanning electron microscopy revealed on the surface of the carbonates small (100 nanometers) ovoids and elongated features. Similar textures have been found on the surface of calcite concretions grown from Pleistocene groundwater in southern Italy, which have been interpreted as representing nanobacteria.
    • The isotopic composition of the carbonates, and the new data on the magnetite and iron-sulfide particles, imply a temperature range of 0' to 80'C, cool enough for life.

"When considered collectively ... we conclude that [these phenomena] are evidence for primitive life on early Mars."

Statement of Joan Oró, Microbiologist and former NASA consultant:
"Dazzled, scientists that say they have found life in Mars, have blundered"

Mars and martian meteorites

Earth-Mars

martian lake
Martian lake

 Today Mars is a little dry planet. It's too cold and its atmosphere is too thin to bear life.

But early in its history, conditions were warmer and wet: identical to those under wich life started on Earth.
Diameter:
6,794 Km (53% of Earth)
Mars Day:
24hrs 37 min
Mars Year:
687 Earth Days
Mass:
11% of Earth
Gravity:
58% of Earth
Atmosphere:
95% CO2, 3% N2
Atmospheric Pressure:
1% of Earth
Temperature:
-140 to 20º C

Mars
Valles Marineris

ALH84001
ALH84001

Apollinaris Patera
Apollinaris Patera

 Most of the many meteorites that fall in our planet come from collisions between asteroids. But a few, that we call SNC (snics), are different in composition and origin: their minerals crystallized under the same conditions of the Mars' environment.
The abundance and composition of the trapped gases in the SNC meteorites have an almost exact correlation with the measured atmospheric composition on Mars by the Viking landers.

The Allan Hills 84001 (ALH84001) meteorite, the oldest of the 12 meteorites identified as having come from Mars, crystallized from molten rock about 4.5 billion years ago, early in the planet's evolution. It is the only Martian meteorite to contain significant carbonate minerals. ALH84001 is riven with tiny fractures resulting primarily from impacts that occurred while the rock was on Mars. The secondary carbonates formed along with some of these fractures, about 3.6 billion years ago, when some water squeezed into the cracks, and perhaps tiny bacteria as well.

There are many big volcanos on Mars, but they doesn't seem to be the origin of martian meteorites. About 1.5 million years ago, a major asteroid impact on Mars threw ALH84001 into space, where it eventually fell onto an ice field in Antarctica about 13,000 years ago. ALH84001, which shows little evidence of terrestrial weathering, was discovered by meteorite-hunting scientists in 1984 and only recently identified at Martian.

Alan Hills are one of the best places to find meteorites: After their fall, preserved and engulfed in the antarctic ice, they are conveyed to the surface after a long trip. Wind erosion makes the rest. There are no many rocks around to mix up with!