There’s definitely life on Mars. We sent it there.

Oops. Mankind’s inadvertent colonizing of Mars, with bacteria from Earth.

56 years ago, in May 1961, President Kennedy famously proposed to Congress that the US should commit itself, “Before the decade is out, [to land] a man on the Moon and return him safely to the Earth.”

Eight years later – and a mere five months before the Presidential deadline – Apollo 11’s lunar landing module settled itself on the moon’s dusty surface, and astronaut Neil Armstrong became the first human to step out onto it.

A mere three years after that, when Helen Reddy’s “I Am Woman” topped the Billboard Hot 100, Apollo 17’s Eugene Cernan became (still) the most recent human on the moon, leaving it behind on December 14, 1972 to return to Earth.

Five of the six Apollo missions during those three short years successfully landed on the moon (Apollo 13 being the one exception), conducting a ton of experiments, a couple of which involved bacteria.

In fact, when an incredibly thorough 2010 review of space microbiology was published, there were only two occasions on which bacteria had been exposed to space conditions, and these were both during the Apollo 16 and 17 missions.

If you were a microorganism, you’d find space a ridiculously inhospitable place.

You’d experience intense radiation fields, high vacuum conditions, extreme temperatures, and on top of it all, microgravity.

So, the next time you’re tempted to complain about your morning commute, be glad you’re not a bacterial cell in space.

When a range of microorganisms were deliberately exposed to space conditions, only a couple of species of lichens were able to maintain full viability after two weeks – Rhizocarpon geographicum and Xanthoria elegans.

Everything else was killed off, mainly by the intense solar UV radiation.

Interestingly, however, when experimenters shielded samples from radiation, one species of bacteria – Bacillus subtilis – was able to survive in spore form in space conditions for up to six years, especially when it was embedded in clay, or placed in what scientists described as artificial meteorites, made from meteorite powder.

Now, making your own meteorites by grinding up, well, meteorites did rather put us in mind of a cake recipe that begins, “Take one cake…” but we do kind of get where they were coming from.

Anyway, for most microorganisms to survive in space requires them to be shielded from these harsh conditions, which is of course the case here on Earth, where terrestrial life in our biosphere has evolved for over three billion years, protected by our atmosphere’s security blanket.

Since the earliest days of space exploration, scientists (and tabloid newspaper editors) have been greatly concerned about astronauts accidentally bringing extra-terrestrial microbes back to Earth, and also fearful that humans might contaminate outer space.

Actually we’ve already blotted our copybook in terms of the latter.

In 1971, ironically the same year that David Bowie released his song “Life On Mars,” the unmanned Soviet Mars 2 lander crashed on the Martian surface, almost certainly resulting in the release of bacteria, some of which is likely to have survived, despite the harsh environmental conditions on Mars.

Other Mars missions have added to the bacterial life that man has already “introduced” to the planet, with the net result that NASA has had to declare exclusion zones on the Mars surface, euphemistically known as “special regions” that the Opportunity and Curiosity rovers are prohibited from visiting, due to the likelihood of them being inhabited by microorganisms we sent there.

Hopefully their impact will be minimal, but it does make you appreciate that we need to be really careful in the big “out there.”

This was already a concern 50 years ago when the United Nations Outer Space Treaty of 1967 was signed, including an agreement to protect space and celestial bodies from Earthly contamination.

NASA takes these responsibilities sufficiently seriously to have appointed someone who we think has the world’s coolest job title.

Dr Catherine A. Conley is “Planetary Protection Officer,” which we’d love on our own business cards.

Dr Conley’s responsibilities are vital ones. As she says, “If we’re going to look for life on Mars, it would be really kind of lame to bring Earth life and find that instead.”

What about the threat of microorganisms coming the other way, though?

Could we be infected by killer microbes hitching a ride on meteorites?

Astronomers at Cornell University report that Earth is the recipient of a pretty vast (astronomical?) amount of plummeting material that originated in outer space.

Although the majority is dust-sized, estimates for the mass of material that falls on Earth each year range from 37,000-78,000 tons.

Believe it or not, scientists have simulated the meteoric microbe situation by attaching lumps of rock to the heat shield of a Russian spacecraft, having previously drilled holes in the rocks and loaded them with microorganisms.

As the spacecraft re-entered the atmosphere at 7.7 km/s, the samples became hot enough to melt silica and basalt.

None of the bacterial samples survived, which seems a bit unsurprising, but good to know.

As far as we’re aware, only one person in history has ever been hit by a meteorite and, amazingly, she lived to tell the tale.

So if you’re having the day from hell today, be a little relieved that there’s one thing you can scrub from your list of things to worry about.

Even if you’re unlucky enough to be hit by a falling meteorite, at least your wound is unlikely to get infected by alien microbes.

More reading

How many meteorites hit Earth each year?

Mars Is Pretty Clean. Her Job at NASA Is to Keep It That Way.

Office of Planetary Protection

Space Microbiology

The Hot 100 – 1972 Archive

The True Story of History’s Only Known Meteorite Victim

United Nations Treaties And Principles On Outer Space

What Happens to Spores in Space?