Life on Mars? Martian Meteorites, Martian Microbes

Part (i) of a two-part look at bugs in space.

Just over a week ago, six scientists checked out of a 1,200-square-foot dome high on a Hawaiian mountain after living in it for a full year, in order to simulate a mission to Mars.

Their conditions weren’t the kind of sterile ones that might be demanded in a real space mission.

In fact we know they were definitely accompanied by bacteria (other than those they carried in their own microbiomes) because among other things their fascinating blog reports that the “Aloha-nauts” baked their own bread using a sourdough starter, and also fermented yogurt, both requiring the presence of bacteria of course.

Apparently they were also collecting human bacteria specimens for later laboratory analysis.

(This was a Mars experiment, mind, so no jokes about Uranus please.)

However, it got us thinking about bacteria and space, leading to some fascinating learning which we’ll actually need to spread across two weeks.

Standby for takeoff.

Let’s begin with a controversial claim made in 1996 that a meteorite found in Antarctica seemed to suggest there could have once been bacteria on Mars.

Whoa.

Meteorites in Antarctica?

From Mars?

Yup, this raises so many questions, with so many incredible answers.

To date, around 61,000 meteorites have been found on Earth, of which 132 have been identified as Martian.

Scientists know this by identifying traces of the Martian atmosphere in these peculiar rocks from space.

They suggest that Mars was struck by a huge comet or asteroid about 16 million years ago, flinging rocks with sufficient force to escape the planet.

The particular potato-sized rock founded in Antarctica in 1984 is believed to have spent millions of years floating through space, before encountering Earth’s atmosphere about 13,000 years ago, falling to earth in Antarctica as a meteorite.

Its Martian origin was recognized in 1993 then, three years later, scientists announced to the world that they’d identified the fossilized remains of bacteria within the structure of the rock.

They hypothesized that the rock had split open whilst on the surface of Mars, then water had crept into the cracks, and become colonized with bacteria.

Well, that was the theory.

A lively and planet-sized debate ensued, the balance of opinion suggesting that curious microscopic spherical and tubular structures in the meteorite weren’t actually bacteria.

That’s not to say there definitely weren’t ever bacteria on Mars, just that this particular meteorite didn’t contain evidence of them.

Meteorites fall pretty randomly across the Earth’s surface, but Antarctica has proved to be a perfect place to gather them.

The Antarctic Meteorite Program, funded by the National Science Foundation among others, sends a team of scientists to gather meteorites once a year.

And since 1978 they’ve collected almost 22,000, with one visit alone turning up 569 meteorites in two weeks.

In fact, on one extraordinary day in December 2014 the team gathered 170 specimens.

But why on Earth (ha!) should Antarctica be such a great place for meteorite hunters?

After all, surely there’s just as much chance of a meteorite landing in Times Square as there is in a Times Square-sized piece of the Antarctic?

Well, Antarctica acts as a kind of meteorite funnel.

When these space-borne projectiles land on high altitude ice-fields, they get covered with snow, then begin an incredibly slow downhill journey across Antarctica, taking hundreds of years.

But they’re brought to an abrupt halt by natural barriers, such as mountains.

Then wind erosion causes the meteorites to rise to the surface, where they’re easily spotted against the white snow, by eagle-eyed scientists,.

Although the 1984 meteorite probably doesn’t contain fossilized bacteria, more recent findings from NASA definitely suggest that we shouldn’t discount the possibility of the red planet having once been home to microbial life.

In December 2013, NASA reported that the Curiosity rover had discovered that Gale Crater, where the rover landed, once contained a freshwater lake, in which microorganisms could well have existed.

So that’s Mars, then, along with what I hope you’ll agree has been a fascinating diversion through the world of Antarctic meteorites (as opposed to Arctic Monkeys).

And as I said at the top of today’s post, we turned up a ton of out-of-this-world bacterial stories, so more next Monday.

Watch this, uh, space.


Further reading

Ancient Martian Lake May Have Supported Life

ANSMET

Antarctic Meteorite Collection

Antarctic Meteorite Newsletters

Antarctic Stations – NASA

Bacteria surfing space – Walking on Red Dust

Space rock re-opens Mars debate

Live From Mars – 12 months, 6 scientists, 1 dome.

Mars Meteorite Home Page (JPL)

Martian meteorite

Meteorite Yields Evidence of Primitive Life on Early Mars

Special Collection – Curiosity

UCSB Science Line

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