Got Aliens in Your Nose?

This week the Royal Society in London is holding a two day meet-up for scientists to talk about the state of our search for extraterrestrial life.

At a lecture today, astrobiologist Paul Davies of Arizona State University told the crowd that he thinks aliens already walk among us. Well, maybe not walk—more like float, or wiggle, or however else bacteria may locomote.


AHHH!!! It’s an invasion!

—Buggy artwork by Jane Hurd, NGS

According to the Associated Press, Davies thinks that life from elsewhere in the galaxy has made its way to Earth at several points in human history. It’s possible, he says, that alien life is “right under our noses—or even in our noses.”

And why not? So many science-fiction writers seem convinced that if aliens of any shape or size were to come to Earth, they’ll be bad for humans and hence immediately noticable. Giant robots! Predatory stalkers!! Killer pathogens!!! Yes, Michael Crichton, I’m looking at you.

But that certainly doesn’t have to be the case.

For starters, consider the odds of an intelligent race of beings existing elsewhere in the universe.

One of the more popular tools for this thought experiment is known as the Drake Equation, proposed by radio astronomer Frank Drake in 1961. The equation goes like this:

N = R* • fp • ne • fl • fi • fc • L


N = the number of civilizations in the Milky Way galaxy with which we would be able to communicate

R* = the rate of formation of stars suitable for the development of intelligent life

fp = the fraction of those stars with planetary systems

ne = the number of planets, per solar system, with an environment suitable for life

fl = the fraction of suitable planets on which life actually appears

fi = the fraction of life bearing planets on which intelligent life emerges

fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time such civilizations release detectable signals into space

Critics point out that some of the values for this equation are either constantly being revised or are near impossible to measure right now (imho, see fl, fi, fc, and L).

That means any solution would be based on pure speculation and therefore would hold little scientific value.

Still, if you fill in the equation with educated guesses, values for N range from 5,000 to 2.3.

I’d add to that equation some variables for whether the aliens we ping have invented faster-then-light travel and decide to pop by for a quick hello?

Now consider the likelihood of a few hardy bacteria hitching a ride on an asteroid, and some parts of that space rock somehow raining down on Earth.


Ida: asteroid or alien “spaceship”?

—Image courtesy NASA/JPL

Known Earthly microbes can achieve some pretty amazing feats of survival, from withstanding millennia in ice to “resurrecting” their DNA after intense radiation blasts.

And just think of all the meteorites that have come crash landing in a field or through the roof of a doctor’s office, any of which could have been carrying galactic hitchhikers.

What’s more, the rocks themselves don’t even have to make it to the ground for their components—and maybe their cargo—to seed our atmosphere.

Finally, of the scads of Earth-based bacteria, less than one percent are known to causes diseases in people, according to the Mayo Clinic. That tells me it’s entirely plausible for any alien microbes that make it to Earth to be perfectly harmless, and thus better able to wander around undetected.

All told, I’m with Davies, and I’d wager that simple organisms such as benign bacteria will be the first aliens we encounter on our home turf.

Anyone want to take me up on that bet?

Human Journey