The Cassini mission that has investigated Saturn since 2004 has revealed much about the giant planet and its many moons. Perhaps most tantalizing is the discovery that the moon Enceladus is the source of strong geysers ejecting plumes of water and ice.
A new study of Cassini data published in Nature by Hsiang-Wen Hsu and colleagues reveals these plumes are laced with grains of sand. This indicates that hydrothermal activity may be at work in Enceladus’ sub-surface ocean, and propels this tiny moon into the extremely exclusive club of locations that could harbor life.
The club’s only current member is Earth, of course – although it’s very possible that Europa, one of Jupiter’s moons, is, like Enceladus, also a candidate. What they have in common is that they host liquid oceans of salty water that exists in contact with a rocky, silicate seabed from which the oceans can absorb complex minerals and elements.
Earlier this month, when a few high-traffic news websites reported a strange object or wedge-shaped craft on Google Moon, I was skeptical. Surprised, too, because when I opened the application, there it was, a distinct V-shape of bright lights inside a tiny crater on the moon’s far side. It did not look natural. I marked its location at 142 degrees and 34 minutes east and 22 degrees 42 minutes north, at the edge of Mare Moscoviense.
In 2007, astronomer Duncan Lorimer was searching for pulsars in nine-year-old data when he found something he didn’t expect and couldn’t explain: a burst of radio waves appearing to come from outside our galaxy, lasting just 5 milliseconds but possessing as much energy as the sun releases in 30 days.
Pulsars, Lorimer’s original objects of affection, are strange enough. They’re as big as cities and as dense as an atom’s nucleus, and each time they spin around (which can be hundreds of times per second), they send a lighthouse-like beam of radio waves in our direction. But the single burst that Lorimer found was even weirder, and for years astronomers couldn’t even decide whether they thought it was real.
The burst belongs to a class of phenomena known as “fast radio transients” – objects and events that emit radio waves on ultra-short timescales. They could include stars’ flares, collisions between black holes, lightning on other planets, and RRATs – Rotating RAdio Transients, pulsars that only fire up when they feel like it. More speculatively, some scientists believe extraterrestrial civilizations could be flashing fast radio beacons into space.
Astronomers’ interest in fast radio transients is just beginning, as computers chop data into ever tinier pockets of time. Scientists call this kind of analysis “time domain astronomy.” Rather than focusing just on what wavelengths of light an object emits or how bright it is, time domain astronomy investigates how those properties change as the seconds, or milliseconds, tick by.
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.