ALH84001 – Planet Pailly

You remember that meteorite from Mars? The one that purportedly had fossilized Martian microorganisms inside it? The controversy over that meteorite has never been fully settled. And now, it’s not just one meteorite. Now there are two of them.

That original meteorite was named ALH-84001. Names are important. You can learn a lot simply by understanding where a name came from. The name ALH-84001 tells us a bit about this particular meteorite’s history. It was found in the Allan Hills region of Antarctica (ALH) during a 1984 scientific expedition (84), and it was the first meteorite found by that expedition (001).

This new meteorite is named ALH-77005, so right there you know some important things about it. It was found in the same region of Antarctica, a few years before ALH-84001. And like ALH-84001, ALH-77005 sat in storage for a while before anyone got around to examining it. In fact, it sounds like ALH-77005 has been sitting in storage for a whole lot longer than ALH-84001 did.

When I first heard about ALH-77005 and the surprises that were found inside it, my initial reaction was enthusiastic. Surely this would bolster the Martian fossil hypothesis for ALH-84001, I thought. But after some of the research and having some time to think, I don’t think this new evidence actually changes anything.

It’s still possible that something happened to ALH-84001 once it landed here on Earth. For example, maybe Earthly microorganisms somehow wormed their way inside the rock. If so, the exact same thing may have happened to ALH-77005. So have we found new evidence of life on Mars, or new evidence of life in Allan Hills? There’s still no way to tell for sure.

But it does make you wonder: how many more meteorites are just sitting in storage, waiting to be opened up?

Welcome to a special A to Z Challenge edition of Sciency Words! Sciency Words is an ongoing series here on Planet Pailly about the definitions and etymologies of science or science-related terms. In today’s post, B is for:

B.S.O.

When you study the planets, when you really get to know them well, you soon start to feel like they each have their own unique personalities. Jupiter is kind of a bully, pushing all the little asteroids around with its gravity. Venus hates you, and if you try to land on her she will kill you a dozen different ways before you touch the ground. And Mars… I can’t help but feel like Mars is kind of jealous of Earth.

I get the sense that Mars wishes it could be just like Earth, and that Mars is trying its best to prove that it has all the same stuff Earth has.

In 1996, Mars almost had us convinced. A team of NASA scientists led by astrobiologist David McKay announced that they’d found evidence of Martian life.

As reported in this paper, McKay and his colleagues found microscopic structures (among other things) within a Martian meteorite known as ALH84001. They interpreted those structures to be the fossilized remains of Martian microorganisms.

This was a truly extraordinary claim, but as Carl Sagan famously warned: “extraordinary claims require extraordinary evidence.” Or to put that another way, when it comes to the discovery of alien life, astrobiologists must hold themselves and each other to the same standards as a court of law: proof beyond a reasonable doubt.

In follow-up research, those supposed Martian fossils came to be known as bacteria shaped objects, or B.S.O.s for short. I kind of wonder if somebody was being a bit cheeky with that term. I wonder if someone was trying to say, in a subtle but clever way, that the whole Martian microbe hypothesis was just B.S. As this rebuttal paper explains:

Subsequent work has not validated [McKay et al’s] hypothesis; each suggested biomarker has been found to be ambiguous or immaterial. Nor has their hypothesis been disproved. Rather, it is now one of several competing hypotheses about the post-magmatic and alteration history of ALH84001.

In other words, those B.S.O.s might very well be fossilized Martian microorganisms. Yes, they might be. It is possible. But no one has been able to prove it beyond a reasonable doubt, and therefore no one can say with any certainty that we’ve found evidence of life on Mars. At least not yet.

Still, the ALH84001 meteorite and its B.S.O.s are an important part of the history of astrobiology. As that same rebuttal paper says:

[…] it will be remembered for (if nothing else) its galvanizing effect on planetary science. McKay et al. revitalized study of the martian meteorites and the long-ignored ideas of indigenous life on Mars. It has brought immediacy to the problem of recognizing extraterrestrial life, and thus materially affected preparations for spacecraft missions to return rock and soil samples from Mars.

Next time on Sciency Words A to Z, are we prejudiced against non-carbon-based life?