Fossils -- Out of This World

Science is awash with fascinating ideas and questions, so much so that I find it hard to keep any focus at all. My most recent tangent draws its momentum from recognition that the fossil record is a record of some of the life that has existed on Earth, with an emphasis on Earth. But, the actual igniting spark for this tangent was provided by an amateur astronomer when he introduced me to the Drake Equation. This opened up an exciting literature of stimulating and competing logical propositions and arguments.

Astronomer Frank Drake proposed his formula as a way of estimating the extent of the presence of intelligent life in the galaxy. Its proximate genesis was a meeting he convened in 1960 at Green Bank, West Virginia, to explore the issue of detecting intelligent life across the vast distances of the galaxy.

I realized a few day[s] ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it’s going to be to detect extraterrestrial life. And looking at them it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy. This, of course, was aimed at the radio search, and not to search for primordial or primitive life forms. [Link here]

In the almost 50 years since, the search for extraterrestrial intelligence (SETI) and the debate over the likelihood of its success has waxed and waned. Of particular interest to me is that paleontology has been involved in this effort, used by some as a brake on expansive claims about a profusion of intelligent life spread throughout the galaxy. The paleontological history of the Earth is one punctuated by mass extinctions, leading some to argue that the rise of intelligent life here wasn’t inevitable, just extremely fortunate. As a result, in their view, the chances of intelligent life elsewhere are mighty slim. [Link here]

But, even some in that camp see the odds of there being primitive life in the galaxy as something else altogether – pretty good, as a matter of fact.

I’m slow on the uptake, so, I came late to the realization that the search for extraterrestrial life (intelligent or not) includes the pursuit of fossil evidence of that life. What a prospect! And what a daunting challenge given the difficulties of identifying fossils from our own planet, much less finding them here in the first place! Still, it seems compelling to make the search and it’s probably not a pipedream. Astrophysicist Neil deGrasse Tyson writes:

The discovery of simple, unintelligent life forms elsewhere in the universe (or evidence that they once existed) would be far more likely and, for me, only slightly less exciting than the discovery of intelligent life. Two excellent nearby places to look are the dried riverbeds of Mars, [where] there may be fossil evidence of life from when water once flowed, and the subsurface oceans that are theorized to exist under the frozen ice layers of Jupiter’s moon Europa. [Link here]

A little more than two weeks ago, on March 6, 2009, the search for life elsewhere in the galaxy took a significant step forward with the launch of the Kepler spacecraft. Kepler will function, according to NASA, as a “giant camcorder” staring at the same 100,000 stars for at least three and a half years, seeking subtle traces of planets up to the size of the Earth in the so-called habitable zone around those stars. [Link here] (Crudely, the habitable zone is the area around a star in which a planet might have the conditions supportive of life such as that found on Earth.)

But Kepler’s launch is not really action on the fossil front. The Mars rovers are currently where any possible exo-Earth fossil action might be, however unlikely. The rovers were not designed to search out fossil evidence of life, yet, hope springs eternal. David Morrison, senior scientist at NASA’s Astrobiology Institute, wrote early in the Mars rovers’ mission,

With their excellent camera systems, the rovers might indeed see a large fossil of a multicelled creature, if one should happen to be there, but this is extremely unlikely – think how difficult it is to find macroscopic fossils [on] Earth, a planet where multicellular life has been abundant for hundreds of millions of years. [Link here]

That improbability hasn’t stopped some segment of the general public from thinking it sees fossils in images beamed back by the hardy rovers – yes, their claims have a tabloid feel to them. Nevertheless, it’s an exciting pursuit and I’m rooting for the rovers on Mars today. I’m also rooting for a future Mars rover mission to have some element designed specifically for that kind of exploration.


Microscopic look at Mars soil aboard Mars Rover Opportunity.
Image Credit: NASA/JPL/Cornell