Meteorites from Mars
While we've been to Mars with the Viking Mission
and sampled the soil, no mission has returned with rocks from
Mars. Luckily, nature has brought a few
to us! This has given us crucial information. To the right
is the famous Martian Meteorite, ALH84001 (we'll go over this
more next lecture)..
Twenty-four meteorites have been identified as coming from Mars. How do they (scientists) know that?
- 1) They are very young igneous rocks, < 1.3 b.y.o.
Asteroid/Comet meteorites formed when the Solar System formed
(4.5 b.y.o.).
2) Since they represent recent formation, they must have
come from a planet which could support volcanism in the
last billion years. Only Venus, Earth, and
Mars are big enough to still have internal Heat.
- Why MARS? Gases trapped in a few of these meteorites
show the exact same unique isotopic
ratios as found in Mars' atmosphere by Viking mission --->
These meteorites are sometimes called SNC (pronounced, `snick') for the first three of these types found (Shergotty, Nahla and Chassigny, found > 100 years ago). Like to own a piece of Mars? The Zagami Meteorite is among the most easily obtained of the Mars meteorites. Check this out.
How did rocks from Mars get here? Impacts drove them off with great velocity from the Mars surface (need 5.4 km/s to escape Mars' surface).
What have they told us? A few show water in them. Others show crystals or clay sediments, from interaction with water. Comparing the ages of the rocks with the gases contained, it tells us about the development of Mars' atmosphere, and how it lost its light elements quickly, a different evolution than occurred on Earth.