Titanic Voyage Reaches Its End
After traveling through more than 2 billion miles of space, the European Space Agency's Huygens probe reached its final destination early Friday, NASA said. It successfully navigated the murky atmosphere of the Saturn moon Titan and touched down on the moon's surface two and a half hours later, at 2:25 a.m. PST.
Scientists hope it snapped photos as it landed and began snatching up souvenirs, just like any other tourist.
Space scientists were emotional as they reported the apparent successful end to a 25-year effort.
"We have a signal, meaning that we know that Huygens is alive, so the dream is alive," said an ESA director general Jean-Jacques Dordain. "Alive for time enough to say certainly this is an engineering success, and we shall see later this afternoon if this is a scientific success."
The ESA confirmed that the Green Bank Telescope in West Virginia picked up the first signal, and a telescope in Australia later picked up a second signal. An ESA official also confirmed that the probe likely deployed at least two of the three parachutes.
Huygens sent a "feeble" signal, indicating it was still alive. Scientists compared it to the tone on a telephone handset that indicates it's working.
Watch animations depicting potential landing scenarios for ESA's Huygens probe.
• Sea landing
• Surface landing
Because the probe is so far away, one official described the search for a signal as much more challenging than looking for a needle in a haystack.
Now researchers are hoping to retrieve useful data that Huygens will send to Cassini, which doubled as Huygens' ride until Dec. 25, when the 700-pound probe was cut loose to drift to Titan's surface.
It takes one hour and seven minutes for the signal to travel from Cassini to Earth. The European Space Agency hopes to see the first of its images Friday afternoon, and will release photos to the public soon after. "It's a very exciting time, waiting for that first data to come back from Huygens," said Linda Spilker, who has worked on the project since 1988.
It will be the closest look scientists have ever had at Titan, which they believe is similar to a very young, though much colder, Earth. Researchers hope studying the moon will reveal how the Earth formed. Scientists tried to use radar from Cassini to find out more about Titan's surface, but the moon's atmosphere is so thick they could discover only that the surface has rough and smooth surfaces.
If the landing went as planned, Huygens hit Titan's atmosphere at more than 13,000 mph. Three minutes later, at an altitude of about 106 miles and with the probe's heat shield warmed to about 3,600 degrees Fahrenheit, the first of three parachutes deployed. Next, the main chute opened, causing the heat shield to fall away and exposing Huygens' sensors, allowing them to take in samples.
"If the heat shield doesn't come off we won't be able to do much," Spilker said.
The main chute fell away about 15 minutes later and a third, smaller chute should have opened. As it drifted to the moon's surface, Huygens hopefully gathered data on the composition, density and volatility of Titan's atmosphere, took photographs in multiple directions, and recorded sounds.
"The interesting thing is we don't know if it's going to land in a liquid, like a lake of hydrocarbons or a goopy, sticky surface, or ice that will be rock hard," Spilker said.
Officials said they believed Huygens made a soft landing.
The most problematic scenario would have been a landing on a steep incline that pointed Huygens' antenna away from Cassini.
About four and a half hours after the probe lands, the Cassini orbiter will disappear over Saturn's horizon, and Huygens' batteries will begin to die.