It’s almost official. On November 10, NASA announced that it had lost contact with the Phoenix Mars Lander, which effectively marked the end of a spectacularly successful mission on the Red Planet. As I write this, engineers at JPL in Pasadena, CA, are monitoring the spacecraft to see if its solar arrays can collect enough sunlight to allow it to call Earth one more time. But this isn’t likely, because Phoenix is in Mars’s north polar region, and the Martian winter is already in full swing. There isn’t much sunlight reaching the pole these days.
Over its five-month-long mission on the surface – two months longer than expected – Phoenix accomplished something unprecedented in the history of humankind’s investigations of Mars: it verified the presence of calcium carbonate, an indicator for liquid water and, using its robotic arm to dig, identified two different types of water-ice deposits beneath the planet’s surface.
The data collected by its sophisticated instruments and cameras will be studied for decades, but already scientists know the arctic region has soil that is mildly alkaline and contains salts that could serve as nutrients capable of supporting life. In sum, the Phoneix mission has brought scientists several steps closer to determining if the Martian polar region is -- or ever was in the past -- conducive for microorganisms.
On Earth we’ve known about them since the mid-17th Century (does the name van Leeuwenhoek ring a bell?), but in recent decades new ones have been discovered in some the harshest places on our planet.
One recent discovery was announced this past summer at the annual meeting of the American Society for Microbiology. Jean Brenchley and Jennifer Loveland-Curtze, two researchers from Pennsylvania State University, described a new species of bacteria from Greenland that is so small it easily passes through today’s commonly used microbiological filters. These “ultra-small cells” are turning-up in surprising places. The Greenland bacteria were found living nearly two miles below the surface, encased in glacial ice that was determined to be about 120,000 years old.
These and other extremophiles have been found in a suprisingly wide variety of unforgiving environments on Earth: low-oxygen, no-oxygen, high-pH, low-pH, no-light, high-pressure, etc. In 2006, a team from Princeton University found bacteria that obtain all their nourishment from hydrogen and sulphur compounds derived from naturally decaying radioactive rock. These also live about two miles below ground, in South Africa.
Apart from sometimes being amazingly tough creatures, microorgamisms constitute a major proportion of life on Earth. According to Loveland-Curtze, "Microbes comprise up to one-third or more of the Earth's biomass, yet fewer than 8,000 microbes have been described out of the approximately 3,000,000 that are presumed to exist."
So many microbes, so little time, as the microbiologists say.
But for me, what’s really intriguing about the extremophiles we’ve discovered here is the prospect of analog microorganisms living beyond Earth, perhaps in our own solar system.
Probably the most thought-provoking – and certainly entertaining – book I’ve read on this subject is David Grinspoon’s Lonely Planets: The Natural Philosophy of Alien Life, which won a Pen Center USA literary award when it appeared in 2004. I highly recommend it (see sidebar). Grinspoon is a planetary scientist and Curator of Astrobiology at the Denver Museum of Nature & Science. In Lonely Planets he not only effectively presents the big picture on a wide range of subjects that pertain to how we think about life on and off our planet – microbial as well as complex forms having (dare I say it?) “intelligence” – but he also reminds us of the value that natural philosophy, or a natural philosophical approach, can bring to the subject.
Natural philosophy will be explored in future posts. It’s worth several stops, in fact.
BTW, Grinspoon's site is worth a visit, too.
Meanwhile, Phoenix sits silently on the Martian arctic plain, buffeted by winter winds in near-dark conditions. I applaud the lander’s many accomplishments, but I also wonder if something similar to, but different than, an Earth-bound microorganism occupies a void in the rock and ice a mile or more beneath its frozen footpads.
Perhaps we need to dig deeper.
Next stop: More good reads
Banner bus photo created by Dorothy Delina Porter