Looking For the Conditions For Life on Mars & the Gas Giants' Moons

For the first time ever, a robot has drilled into a rock on another world. On Saturday 9th February 2013, Curiosity's  science team announced not only that official drilling has begun, but that all of Curiosity's instruments have now been tested and used, and she is fully functional.  NASA's Science Mission Directorate associate administrator, John Grunsfeld, said, "The most advanced planetary robot ever designed is now a fully operating analytical laboratory on Mars. This is the biggest milestone accomplishment for the Curiosity team since the sky-crane landing last August, another proud day for America. 

conditions1Mars image credit:  NASA/JPL-Caltech/LANL/CNES/IRAP/LPGNantes/CNRS. Earth image credit: L. G. Lyon.

The chosen rock has been named “John Klein”, after a NASA team member who died a couple of years ago. It's a sedimentary rock thought to have a watery history. We already know that Curiosity's area on Mars was once very persistently wet, with sedimentary rocks all around that were deposited in cycles of wetness and evaporation. The light-toned veins you can see here (above and to the left) are calcium sulfate deposits within the John Klein rock, another huge indicator of water. The picture on the right is a patch of Egyptian rock from Earth with veins of calcium sulfate running through it

conditions2The drill hole in the middle is from the first official drill. The one on the right is from a test drill, done last week. The science team took their time testing all components of the drill, so that they would know what to expect in this rock when the first official drill was performed.
Image credit: NASA/JPL-Caltech.

Curiosity has just passed her 6-month anniversary on Mars, and she has already found some amazing geology - amazing because of its likeness to a lot of geology on Earth! Still, there have been some impatient murmurings from certain Earthlings, who are frustrated at Curiosity's slow and methodical pace since the excitement of the landing. And let's face it - unless you're a tech geek, it's hard to whip up enthusiasm for a little drill making a tiny hole into a stone. But think what this means. Curiosity's drill will be boring several centimeters (about 2 inches) into rocks and we'll be able to “see” what chemicals are inside Martian rocks thanks to her spectrometers. We'll be able to look back through time to see whole stretches of rock-water history in Gale crater. And her exploration and findings have actually moved really quickly - she found water-formed rocks almost right after she landed last August, and took pictures of an ancient, now-dry stream bed. Astrobiologists were pretty happy when she  beamed these pictures back to Earth, because Mars was looking more and more like it had been very wet when young. Curiosity's mission is to see if Mars could have once been a habitat where life as we know it could have lived, and in just her first half a year she has found major signs of a past that was salty and consistently wet, with water processes that we easily recognize from Earth.
 
The two Martian rovers that landed in 2004, Spirit and Opportunity, found lots of evidence that Mars had been watery in places for very long lengths of time. They found sulfate minerals that had been formed from mineral-laden water, and at Opportunity's site the robot found other water-related minerals that had later filled in the cracks of the sulfates. On top of this, a big piece of evidence for Martian oceans comes from orbiters around Mars, which can remotely identify some kinds of minerals, geologic features, and elevation. Dozens of places on Mars have what seem to be old deltas around lowlands, where water may have drained from a relatively high place into a body of water. Gaetano Di Achille of the University of Colorado says that if a bunch of these dry deltas form a ring around these lowlands at similar elevations, that would provide good evidence that the lowlands used to be oceans.  On Earth, we have lots of deltas, all at sea level, which drain river water into Earth's oceans. Around half of the old deltas on Mars are at similar elevations to each other, which could mean that they emptied into the lowlands on Mars, at “sea level”.
 

conditions3Oceans may have filled the lowlands in Mars' northern hemisphere, covering possibly a third of the surface.
Image credit: NASA/Greg Shirah.

So if you are impatient for Curiosity to find some exciting rocks, she already has, and she still has a lot more diverse areas to explore! But if you find it more exciting to explore for present-day life off our Earth, you'll love the plans to explore some outer-planet moons. The European Space Agency and NASA, with Russia and Japan, have been making plans to send robotic explorers to the Saturn and Jupiter systems to look for direct evidence of actual life in possible oceans beneath the ice on a few moons, especially Jupiter's Europa and Saturn's Enceladus. Building the explorers will take years because robots need to be developed that can handle the conditions of drilling through kilometers of ice, down to where liquid water probably exists. Also, the various space agencies within joint missions have been working on having their own contributions, like orbiters, function alone, since wobbly funding, especially with NASA, keeps undermining definite plans. But don't worry - icy-moon exploration is a major astrobiology goal, and astrobiologists and engineers are determined to make this happen. It will happen. And part of the focus of the technological designs is meant to get robots through the ice and beaming back results within most of our lifetimes.

Europa

In 2012, the ESA's JUICE mission (the Jupiter Icy moon Explorer) won funding to continue as part of the ESA's Cosmic Vision program. An orbiter to Ganymede and Europa is planned to be launched in 2022, arriving at Jupiter in 2030. Ganymede has a magnetic field, and is thought to have a subsurface ocean. Europa has a water-ice covering thought to be 10-30 km deep, over what is undoubtedly a salty ocean up to 100 km deep and containing twice as much as all the water on Earth put together. The brown streaks (visible in the image above) are most likely where the ice is pulled apart from Jupiter's gravity, letting liquid water and slush get to the surface. There may also be big pockets of seawater within the ice, and if that's the case, it would be much easier for a drilling probe to get to seawater through that thick icesheet.  
 
It's thought that Europa is made up of stuff similar to Earth, with silicate rocks and an iron core. If there is any life in a Europan sea, it would get its energy from minerals instead of sunlight. The surface of Europa is really smooth, with wide flat areas, and this would make it easier to place a lander on the ice. A mission is planned to map the surfaces of Ganymede and Europa in detail fine enough to find a safe place for a lander, and ideally, scientists would like to launch a lander around the same time as the orbiter, so that they can live to see the results.
 
In 2011, NASA launched its Juno mission. The orbiter will study Jupiter itself, and then dive into the planet to die. NASA is purposefully killing the robot when its mission is done, specifically to protect any possible life on Europa from Earth-bacteria carried on the spacecraft. The radiation from Jupiter will be damaging to the orbiter, and even though it has shielding that will let it complete its mission, the human controllers back on Earth could eventually lose control and the orbiter could crash into Europa. Everyone wants to make sure that when humans get a lander and drill onto the Europan ice, the environment will be pristine for a lander's astrobiology mission. Meanwhile, NASA hopes to launch their own Europa spacecraft, the Europa Clipper. This probe would make several fly-bys of Europa, studying the details of the surface ice and underlying water, to prepare for any future landers. If the plans moves forward, the Europa Clipper could be launched in 2021.

conditions5Enceladus, one of Saturn's moons. You can see jets of icy mist erupting from the surface.
Image credit: NASA/JPL.

Enceladus has become the favorite for a lot of astrobiologists. In 2005, the Cassini spacecraft found plumes of ice erupting from the south pole area. So much icy spray is shot into space from Enceladus' interior that the icy mist actually perpetuates Saturn's E-ring. Since finding the jets, Cassini has used its mass and infrared spectrometers several times as it flew through the plumes, and it has found a bunch of really exciting stuff: water, methane, ammonia, simple and complex organics, carbon monoxide and carbon dioxide. The infrared spectrometer detected heat under the ice in the area that produces the plumes. 
 
When astrobiologists consider environments that could possibly support life, they look for four essential things: water, organic carbon, nitrogen, and an energy source. Enceladus has all those things. The heat would provide energy, as well as potentially melting ice into big pockets of liquid water. But the ammonia is a huge find: it could provide the nitrogen necessary for life, and also, it would help lower the freezing point of the water to potentially keep stable liquid environments.

conditions6Molecules found in Enceladus' plumes by Cassini's mass spectrometer.
Image credit: NASA/JPL/Southwest Research Institute.

conditions7Cassini's infrared spectrometer found this hot spot under the features on the left called “tiger stripes”, where the jets of spray come from.
Image credit NASA/JPL/GSFC/SwRI/SSI. 

Engineers are now working on technology to use above and on Enceladus, to be ready when the day finally comes that there is enough funding for the mission. NASA would like to send a probe to fly through the jets and bring back a return sample to Earth, since this would give many scientists the chance to examine the sample in all sorts of ways and verify each other's results. Sample return missions of often seen as the holy grail in terms of analysis, and this technique has already been done: in 2006, the probe in NASA's Stardust mission flew through the tail of Comet Wild 2 and returned to Earth with a sample. It's possible that a sample-return mission could be launched by 2020. And European scientists in the Enceladus Explorer program are working on a heat-drill probe, that will use a combination of heat and drilling to sink down through the ice and reach liquid water. The probe is called Ice Mole, and its experimental drilling and navigation systems are being tested on glaciers and in Antarctica.

conditions8The “tiger stripes” on Enceladus which lie over the heat sources.
Image credit: Cassini Imaging Team/SSI/JPL/ESA/NASA

So almost certainly in the lifetimes of most people reading this, we will have gotten a chance to look directly for present-day life on other worlds in our solar system. Meanwhile, Curiosity and icy-moon probes are helping us know that the conditions required for life aren't rare at all in Sol's part of the galaxy.