I"ve just finished reading about how researchers have concluded the Mars to be never heat based on analysis of a meteor — discovered on earth. More distantly you"ll remember the they to be debating even if it is a fossil the a living organism had actually been discovered in a martian meteor found in Antarctica. My question: how do they understand these meteors came from Mars? room they labeled? have they found meteors from various other planets the they recognize? Why waste all this money and also time top top the an are program if there are rocks from these planets just lying roughly earth?

Kent, Birmingham, Alabama

Illustration by cheese Signorino

Cecil replies:

The rocks were uncovered on earth, Kent, for this reason they’re meteorites, not meteors. (Meteors are room rocks that fried food in the atmosphere; meteorites are the remnants that make it every the way down.) once you get that straight, try chewing ~ above this: scientists think the martian meteorites came from Mars because — ns realize the nontechnical psychic won’t find this entirely persuasive — they can not plausibly have actually come from all over else.

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The Martian meteorites — 34 have actually been established to date — are jointly known as the SNC (pronounced “snick”) group. The letters stand for three associated categories the geologically inexplicable meteorite: shergottites, the prototype that which fell in 1865 near the town of Shergotty in India; nakhlites, named for a rock that dropped top top Nakhla, Egypt, in 1911; and chassignites, therefore called because of the specimen thatlanded in Chassigny, France, in 1815.

For year it to be assumed the the SNC meteorites to be hunks the asteroid favor pretty lot every other space rock. Then in 1979 geologists Hap McSween and also Ed Stolper advanced the watch barmy thesis that the meteorites had actually come indigenous Mars based upon the adhering to logic: (a) the SNC stones were igneous, i.e., volcanic; (b) all examples then known had solidified 1.3 billion years back or less; (c) just planet-sized bodies still had actually volcanoes going the late in the game — earth moon cooled off around 3 billion year ago, and also asteroids chilled soon after their creation around 4.5 billion years ago; (d) the the two planets that can reasonably be claimed to be in ~ a stone’s throw of us, Venus’s solid gravitational pull and thick environment make the an unlikely launching pad for meteors; so (e) the pretty much leaves Mars.

Persuaded? McSween’s other rock jocks at first didn’t buy that either. But then various other researchers analyzed the minute balloon trapped in a shergottite meteorite, i m sorry presumably to be a trace of the setting of the rock’s residence planet. The noble gases in the balloon (argon and such, which being noble don’t change over time and also so space a sort of planetary fingerprint) exactly matched those in the Martian setting as sampled not long before by the Viking landers.

A pivotal question remained: What released the pieces of Martian rock right into space? A monster meteorite strike was the apparent answer, however some objected the the energy of such an influence should have turned the future SNC meteorites into glass or vaporized lock altogether. Two developments helped blunt that argument. The first was theoretical work demonstrating that a percentage of influence debris would (OK, could) survive ejection into space reasonably unscathed, and also the 2nd was the exploration of a lunar meteorite in Antarctica in 1982. (That find, incidentally, addresses your question about whether meteorites from various other planets have actually been discovered. Answer: yes, if you counting the moon. We recognize the Antarctic meteorite came from the moon since it suitable samples brought earlier by the Apollo astronauts.) If a celestial chip shot can blast rocks off the moon, the reasoning went, lock can get blasted turn off Mars, too.

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At this point you might be saying: This is no a story I’d treatment to run previous a judge. Maybe not, however it appears to have brought the work in the scientific community. (You know I’m omitting a many corroborative technical detail.) That’s more than can be stated of the claim that one Martian rock contains fossils of ingredient that as soon as was alive. Follow to McSween, nobody believes this now other than its initial proponents.

That brings united state to your last question: If we’ve obtained the rocks, why go intospace because that more? couple reasons: (1) with all respect come the geniuses who thought it up, few of us would choose a small proof of this cockamamie theory, e.g., an actual Mars rock for comparison. (Conceivably a advanced probe could do the analysis on Mars and also radio earlier the results.) (2) since most Martian meteorites are fairly young, and also the interesting stuff ~ above Mars occurred earlier. OK, possibly the odds that there having actually been Martian life means back as soon as are slim. If that happened, though, i will not ~ you want to know?