The most promising place in the solar system to find life isn't Mars - it's Europa. One of 16 moons orbiting Jupiter, Europa (nine-tenths the size of Earth's moon) has both surface ice and clear signs of a subsurface ocean. An ocean means water, and water means life - especially if, as we suspect, there's a heat source at the moon's core. To get a better look, NASA is planning the Jupiter Icy Moons Orbiter mission to survey Europa and two of Jupiter's other enigmatic moons, Callisto and Ganymede. The launch is planned for 2015. But after the JIMO mission, the real challenge will be to drive a probe through Europa's ice to get a look at the ocean beneath. NASA's probe DepthX is one way to do it (see "To Hell and Back"). Here's another.
credit:Creative Logik-2004 Disney Enterprises, Inc. and Walden Media, LLC
The Journey
The Journey
At its closest, Europa still lies 370 million miles from Earth. To make that commute, NASA will use nuclear-powered ion engines that put the Jupiter Icy Moons Orbiter in position in six years. A follow-up mission will make the first foray to Europa's surface.
credit:Creative Logik-2004 Disney Enterprises, Inc. and Walden Media, LLC
The Descent
The Descent
Once in orbit, the Europa probe will encounter the intense radiation that surrounds Jupiter, so 30 days may be the maximum time to target a landing site. With no atmosphere for parachutes, the lander will use rockets to slow its descent to the surface.
credit:Creative Logik-2004 Disney Enterprises, Inc. and Walden Media, LLC
The Ice
The Ice
The lander will touch down gently in gravity one-eighth as strong as Earth's. But Europa's frozen surface is no low-grav playground; it's constantly quaking and buckling. And there's 5 to 60 miles of shifting ice to bore through to get to the sea underneath.
credit:Creative Logik-2004 Disney Enterprises, Inc. and Walden Media, LLC
The Probe
The Probe
Digging down will require a nuclear-powered "melt probe" - basically a vertical torpedo with a red-hot nose cone. Propelled by gravity, it will melt through the tectonic ice plates. The hole created will freeze up behind the probe as it goes, making this a one-way trip.
credit:Creative Logik-2004 Disney Enterprises, Inc. and Walden Media, LLC
The Breakthrough
The Breakthrough
Due to the time lag transmitting data from Europa to Earth, scientists won't know for 50 minutes whether the probe has broken through. Once on the other side, it will deploy an autonomous underwater vehicle capable of operating independently of both the melt probe and Earth.
credit:Creative Logik-2004 Disney Enterprises, Inc. and Walden Media, LLC
The Deep
The Deep
The AUV will explore Europa's inner reaches, returning to dock with the melt probe to recharge its batteries and uplink data to Earth. It will be searching for hydrothermal activity on the seafloor, the most likely place in the solar system that E.T. would call home.
