What is the endgame in the search for Exoplanets?

Exoplanet illustration via Wired

One of the most interesting areas in Astronomy at the moment is the search for Extrasolar Planets, or Exoplanets.  These are planets that exist outside of the Solar System.  To date, 551 Exoplanets have been confirmed, with the possibility of over 1200 more recently announced by the NASA Kepler team.  Most exciting, a team of French Researchers announced yesterday that they have confirmed that the first exoplanet which could support life has been discovered.

Gliese 581d, first discovered in 2007 with seven times the mass of Earth and roughly twice its size, has a carbon dioxide atmosphere.  This is the first of what could be millions of potentially habitable planets in the galaxy.

Consider that to date, the majority of planets discovered are large gas giants as big or bigger than Jupiter.  It makes sense that as we first look for planets in the cosmos, that we will find the largest of them.  Consider also that several of the popular techniques for detecting planets favor finding planets that have short orbital periods (Kepler has yet to confirm a planet with an orbit longer than 40 days).  As we refine our techniques for planet detection, we will find more and more smaller, Earth-like planets.

The question becomes, then what?

Once a planet is found, we can analyze the light produced as it passes through that planet’s atmosphere to get a rough idea of the gases that make up that atmosphere.  We can tell if a planet has a nitrogen rich atmosphere.  We can also tell how far a planet is from its sun and whether or not it resides in its system’s habitable zone, where a planet can potentially maintain water on its surface.

So in a decade, we’ll have potentially discovered hundreds of planets that could maintain life.  This is where things really start to get interesting.  Once we know a planet could support life, the question becomes is there intelligent life?  Is there a developed society?  On the fringe of things are a couple of researchers who believe we should be able to detect the evidence of asteroid mining.  This would be a sign of a fairly advanced civilization, especially considering we don’t yet have the capability to do that, though I would argue hat’s mainly because we don’t put the money into it.  Once Elon Musk or Jeff Bezos figure out how to reap the profits from asteroid mining, I have no doubt we’ll be there, but that’s another post for another time.

Of course, another possible method of determining if there’s a civilization there will be through just listening.  SETI has been using radio telescopes for years to try to listen for signals from alien worlds.  We have been unintentionally sending signals to space since the dawn of radio.  SETI has been listening for years to see if it could pick up the those signals from another world.  They scan the sky without much guidance as to where to look.  With the discovery of potential life-supporting exoplanets, you now have the ability to do a more guided search.

So, we can discover planets.  We can tell if those planets could support water and whether or not they have an atmosphere.  We have a small chance of being able to tell if there’s an advanced civilization there.  What do we do after we suspect there’s life in them there planets?  Do we just say ‘hey, that’s pretty neat’ and stop there.  I have a hard time seeing that.

I imagine the next step will be what I’ll call the Hawking debate: do we risk alerting a potentially far superior alien civilization to our existence and the risk that they would wipe us out or do we trust that they will be benevolent in their intentions once we send them the “we are here” broadcast.  I do imagine there will be real scientific debate about this, but I think the desire to push the boundaries and explore the universe will win out.

This is where a planet like Gliese 581d becomes really interesting.  Gliese 581d is a relatively scant 20 light years away.  A signal in that direction would only take 20 years to get there and 20 years back.  40 years is a lifetime, but it’s certainly a plausible length of time for an experiment of this magnitude.  Many experiments last for decades or more.  Something like this would be low-cost and low overhead; we would just need to remember to keep listening at the right time.  So we could try to let that civilization know we are here.

So what do we do after that?  Do we send a probe a la the Voyager spacecraft?  Right now, the fastest spacecraft in existence, Helios 2, travels along at a snail’s pace of ~150,000 mph, which doesn’t quite match the 670,616,629 mph that light travels at.  So, without some substantial breakthroughs in the speed of spacecraft, sending any type of probe to Gliese 581d will take a really, really, really, really long time.  My question is, if we know there’s a civilization in this system, is that the impetus needed to devote research dollars to develop new propulsion systems?  Or to go really out there, lead to more research into wormholes, a theoretical mode of travel fairly common in science fiction.

Of course, the ultimate dream would be to actually send someone there, but that’ll have to come after the invention of the wormhole generator and interstellar travel.  So, the best bet for this option may be cryogenically freezing yourself and see how far technology has progressed in about say 300 years.  Maybe then we’ll be able to get a firsthand glimpse of Gliese 581d.  Sure, other science fiction hypotheses exist such as a generation ship, which families would theoretically live in for hundreds of years and cross the cosmos and a more traditional rate of speed, but I’m fairly confident we’re a ways off from that technology, too.

So, we won’t be visiting the alien worlds that are being discovered any time soon, but contact would definitely not be out of the question.  The question there is, should we?