My latest Mind and Matter column in the Wall
Street Journal is on life in space:
A provocative calculation by two biologists suggests that life
might have arrived on Earth fully formed—at least in microbe
Alexei Sharov of the National Institute on Aging in Baltimore
and Richard Gordon of the Gulf Specimen Marine Laboratory in
Panacea, Fla., plotted the genome size of different kinds of
organisms against their presumed date of origin. Armed with just
five data points they concluded that genome complexity doubles
every 376 million years in a sort of geological version of Moore’s
Law of progress in computers.
There are an awful lot of “ifs” in such a calculation. After
all, the increase in complexity could have started fast and slowed
down. Also, it isn’t the first time somebody has suggested
“panspermia,” or microbial life hitching a ride here.
The molecular biologist Francis Crick wrote a whole book called
“Life Itself” on one of these theories that involved intentional
colonization. Crick argued that the universe was already so old
when Earth was born that, if planets are common (check) and life is
probable (still unknown), it was unlikely ours was the first life,
in which case it was likely that advanced civilizations already
existed when Earth was young and that one of them sent microbes out
to seed other solar systems, knowing that the civilization itself
could not manage the trip.
But then, as Enrico Fermi first asked, why have we not heard
radio transmissions from these advanced civilizations? The deathly
silence of the universe remains a paradox.
If it takes 10 billion years to achieve technology and
civilization, Drs. Sharov and Gordon think the spore travelers were
probably launched by accident from a primitive planet, rather than
on purpose from an advanced one. For the same reason, they think
they may have resolved the Fermi paradox, because if it takes so
long to get to our stage of technology, then we may indeed be among
the first to get there. And they predict that we may find life (or
remains of it) on Mars, because we are unlikely to have been the
only landing site for the wandering spores.
Earlier this month the National Aeronautics and Space
Administration announced that its Kepler space telescope has
discovered planets orbiting distant stars in the “Goldilocks”
zone—neither too hot nor too cold for liquid water. Of the three
planets detected, the most Earthlike is probably Kepler-62f, which
is just 40% larger than Earth and orbits a star somewhat dimmer
than our own sun, 1,200 light years from here.
That’s too far away for direct observation, but the planet’s
passage across the face of its sun dims the starlight, so the size
of the planet can be calculated. The ease with which Kepler is
picking such planets up confirms that even small planets with rocky
crusts and tepid-enough surfaces to hold oceans are probably fairly
common in the universe.
Being watery creatures ourselves, depending on the free movement
of soluble substances within our cells, we inevitably expect water
and life to go together. It’s harder to imagine evolution getting
started in a gas or a solid, though perhaps this is aqua-centric.
Anyway, it seems that opportunities even for water-based life may
abound. Does that mean life is common? No. We still don’t know if
it’s very easy or very hard for life to emerge from nonlife even in
the right conditions.
Leave the last word to the Monty Python “Galaxy Song”: “And pray
that there’s intelligent life somewhere up in space / ‘Cause
there’s bugger-all down here on Earth.”