Amy Shira Teitel is a freelance space writer whose work appears regularly on Discovery News Space and Motherboard among many others. She blogs, mainly about the history of spaceflight, at Vintage Space, and tweets at @astVintageSpace.
Last week, NASA announced its next planetary mission. In 2016 the agency is going back to the surface of Mars with a spacecraft called InSight. The mission’s selection irked some who were hoping to see approval for one of the other, more ambitious missions up for funding: either a hopping probe sent to a comet or a sailing probe sent to the methane seas of Saturn’s moon Titan. Others were irked by NASA’s ambiguity over the mission’s cost during the press announcement.
An artist’s rendition of InSight deploying its seismometer and heat-flow experiments on Mars.
InSight is part of NASA’s Discovery program, a series of low-cost missions each designed to answer one specific question. For InSight, that question is why Mars evolved into such a different terrestrial planet than the Earth, a mystery it will investigate by probing a few meters into the Martian surface. The agency says InSight’s selection was based on its low cost—currently capped at $425 million excluding launch costs—and relatively low risk. It has, in short, fewer known unknowns than the other proposals.
But while InSight costs less than half a billion itself, the total value of the mission by the time it launches will be closer to $2 billion. How can NASA get that much zoom for so few bucks? By harnessing technologies developed for and proven on previous missions. The research, development, and testing that has gone into every previous lander take a lot of guesswork out of this mission, helping it fly for (relatively) cheap.
Aside from the Moon, Mars is the only body in the solar system that NASA has landed on more than once. With every mission, the agency learns a little more, and by recycling the technology and methods that work, it’s able to limit expensive test programs. This has played no small part in NASA’s success on the Red Planet thus far. When it comes to the vital task of getting landers safely to the surface, NASA has been reusing the same method for decades. It has its roots way back in the Apollo days.
Only a few decades back, there were serious scientists who thought that planets might be miraculous. Not miracles like a burning bush or a docile teenager, but highly improbable objects. These researchers figured that the conditions necessary for making small, cold worlds could be rare—perhaps extremely rare. Most stars were believed to live their luminous lives alone, bereft of planetary accompaniment.
Well, those thoughts have been banished. In the last 15 years, hard-working astronomers have found many hundreds of so-called exoplanets around nearby stars, and NASA’s Kepler telescope is set to uncover thousands more. (If you don’t know this already, you’ve probably reached this site by mistake. But you’ve come this far already, so keep reading.) Kepler’s principal task is to find habitable exoplanets—worlds with solid surfaces at the right distance from their host star to sport temperatures amenable to the presence of watery oceans and protective atmospheres—planets that might be very much like Earth (depending on some other factors that are harder to measure from light-years away, like geology and chemistry).
Kepler has already found about five dozen candidate objects that, while somewhat larger than our own, seem to meet these criteria. As this space-based telescope continues to peer into the heavens, more such planets will emerge from the data. Indeed, it seems a good bet to guess that at least a few percent of all stars are blessed with “habitable” worlds. That would tally to billions of life-friendly sites, just in our galaxy. This has already prompted SETI scientists to swing their antennas in the directions Kepler’s most promising candidate planets, hoping to pick up the ABCs and MTVs of alien worlds. After all, these systems are arguably the best targets that SETI (the Search for Extraterrestrial Intelligence) has ever had. It’s like discovering a prolific fishing hole.
But there’s a fly in the ointment: While eavesdropping on a small bunch of star systems known to have terrestrial-style worlds is better than taking your chances with random targets, it’s not actually that much better. The reason is simple. The oldest confirmed fossils on Earth are about 3.5 billion years old, and there’s indirect, if sketchy, evidence for life going back 4 billion years. That’s roughly 90 percent of the age of the Earth, which is to say that biology bedecked our planet very early. Life seems to have been an easy chemistry experiment. So that’s yet more encouragement, as it hints that many of those habitable worlds will actually be inhabited. There could be life on billions of planets in the Milky Way.