On Friday, the European Space Agency's Huygens probe will land on the surface of Saturn's largest moon, Titan. The mission hopes to help unravel the mystery of how life evolved on Earth.
Saturn's moon Titan has a dense Earth-like atmosphere
It is in Titan's soupy nitrogen-heavy atmosphere that Huygens will look for clues to uncover the Earth's chemical makeup from over four billion years ago. The high-profile space exploration mission will also mark the first time an unmanned probe lands on an object in the outer solar system.
Once the 320-kilogram spacecraft breaks through the atmosphere, scientists at ESA mission control in Darmstadt, Germany, will use its six specialized instruments to gather data. However, ESA can only guess what is waiting for Huygens on the surface, which could be anything from icy rock to a boggy mush or even a sea of methane.
"The excitement is growing – over seven years of work has gone into this moment," Gerhard Schwehm, ESA's head of planetary science, told DW-WORLD. "Titan is very special. Nobody knows exactly what we'll find there."
Purple haze is seen around the Saturn moon Titan on Tuesday, Oct. 26, 2004 as the NASA/ESA Cassini-Huygens spacecraft makes a fly-by of Saturn's largest moon - the closest ever performed.
The probe got its name from Christiaan Huygens, the Dutch astronomer who discovered Titan in 1655. Larger than either Mercury or Pluto, the moon is the only one in the solar system to have a thick atmosphere. It is thought to be home to chemical reactions and carbon-based compounds similar to ones found on Earth before life existed.
Hitching a ride with NASA
To get to Titan, Huygens hitched a ride on NASA's Cassini probe. Costing $3.2 billion (€2.5 billion), the two have hurtled toward Saturn since their launch in October 1997. But the combined weight of Cassini-Huygens was more than any direct rocket flight could handle. So in order to get to Saturn, NASA sent the spacecraft on a 2.1-billion-kilometer (1.3-billion-mile) journey, including two trips around Venus and one each past the Earth and Jupiter to make use of the planets' gravity for a slingshot effect.
Cassini-Huygens reached Saturn's orbit last summer. Half a year later, the two finally parted ways as Huygens separated and began its approach towards the planet's moon on Dec. 25. But the teamwork didn't end there, as the NASA craft will crucially relay any data collected by Huygens back to mission control.
"We've had flybys before, but this is taking exploration to the next step," Schwehm said, explaining that Huygens' instruments would be looking for complex "pre-biotic" molecules as it enters Titan's atmosphere around 10 a.m. CET on Friday.
A short stay
But Huygens will not enjoy a gentle end to its lengthy journey. During its 140-minute descent by parachute, the probe is likely to be buffeted by strong winds and will face freezing temperatures plunging to -180 Celsius. If it even makes it to the surface intact, Huygens will then begin to survey what Titan is like on the ground.
An artist's impression of the Huygens Probe shortly after landing on Titan. The space probe is due to blast off for Saturn and its mysterious cloud-covered moon Titan Monday October 13 1997,from Cape Canaveral. The Cassini-Huygens mission, a joint venture between NASA and the European Space Agency, is one of the most ambitious space exploration attempts ever undertaken.
However, ESA expects the probe's batteries will only survive for a matter of hours under the harsh conditions. And regardless of how long Huygens holds out, Cassini will no longer be able to receive data from the surface once it disappears beyond the moon's horizon.
"We hope to get the first information around 2 p.m., 3 p.m. (CET)," Huygens project manager Jean-Pierre Lebreton told the news agency AFP.
ESA is hoping for better reception for Huygens on Titan than its last planetary exploration mission. In December 2003, ESA's Beagle 2 lander failed to send back any information after separating from the Mars Express orbiter and touching down on the surface of the red planet.