Two Martians for the price of one


Correa-Martians_vs._Thunder_ChildThe chances of anything coming from Mars are… well quite low, as the song says. So Martian meteorites do tend to get a lot of attention, but none more so than NWA 7034. As discussed in a recent post on my research blog, this new meteorite has an oxygen isotope composition that is very different from all other Martian samples so far identified.

Why is that important?

Well a planet the size of Mars should have melted early in its history and so achieved a fairly uniform isotopic composition. At least that’s what we thought until NWA 7034 came along.

But now the small print!

NWA 7034 is a breccia made up of many fragments of various types of rock. So it could have been produced by the impact of another meteorite into the surface of Mars. Professor Carl Agee and co-workers from the University of New Mexico have argued that this is not the case and that it is more likely that NWA 7034 became fragmented as a result of volcanic processes on the surface of Mars.

So now enter a second Martian sample NWA 7533. At the 44th Lunar and Planetary Science Conference in Houston, Texas Professor Roger Hewins of Rutgers University gave a talk about this sample suggesting that it is an impact rock. Not very surprising you might think. After all, we only have Martian samples because they are ejected into space by a meteorite ploughing into the surface of Mars. But here’s the catch: NWA 7034 and NWA 7533 are paired! That means that they are likely to be bits of the same meteorite collected in the same area of North West Africa. If this meteorite is an impact rock, and not the result of volcanic activity on Mars, then the oxygen isotope data makes a lot more sense.

So now we have one meteorite and two very different views about how it formed. It’s going to be fun seeing how this plays out.

Blog Image credit: Illustration from War of the Worlds by H. G. Wells. drawing by Henrique Correa (image: Wikipedia)


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