NASA Puts Money on Mission to One of Jupiter's Moons

By Joel Achenbach
Washington Post Staff Writer
Wednesday, February 18, 2009; 4:49 PM

Europa, one of the most intriguing objects in the solar system, has won the race to be the highest priority for the next multi-billion-dollar robotic exploratory mission to the outer planets, NASA announced today.

Planetary scientists strongly suspect that Europa, one of the four large moons of Jupiter, has a deep ocean beneath its icy surface. There is speculation that the ocean could contain more liquid water than in all of the oceans on Earth, and that has made Europa a focus in the search for life beyond Earth.

But NASA has also looked at a competing proposal to send a probe to orbit Saturn's huge moon Titan. That moon, currently being observed by the Cassini spacecraft, has dazzled scientists with its lakes of hydrocarbons, methane rain and complex chemistry. Scientists have waited for months to see which moon would get the "flagship mission" status and the money that goes with it, estimated at $2.5 billion to $3 billion.

Europa won the contest. NASA, however, insists that Titan hasn't been shunted aside, and that a probe to Titan remains a high priority.

"Titan will not be forgotten," said Jim Green, director of planetary science for NASA.

NASA's Europa orbiter will be accompanied in the Jupiter system by a European Space Agency probe that will look primarily at a different moon, Ganymede, which may also have a subsurface ocean, and which happens to be the largest moon in the solar system -- even larger than the planet Mercury.

The two probes remain in a preliminary phase and will still need to be funded. In a press release today, NASA officials wrote, "Both agencies will need to undertake several more steps and detailed studies before officially moving forward."

If the money materializes and all goes as currently envisioned, the two probes, collectively known as the Europa Jupiter System Mission, will be launched in 2020. After a six-year cruise, they'll arrive at Jupiter and begin to tour a number of the moons. After two and a half years, NASA's probe will go into orbit around Europa, and ESA's probe around Ganymede. The two space agencies will share data throughout the missions.

"The communities have really come together on both sides of the pond," Green said.

In a conference call with reporters, he noted that it is generally believed that the habitable zone for our solar system is between Venus and Mars. But now scientists believe there may be environments well outside that zone that could potentially harbor life, an idea that Green called "tremendously exciting."

[The NASA news announcement can be found here.]

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