News and Information

Moon data from space probe arrives
January 14, 2005
By Paul Rincon
BBC News science reporter in Darmstadt, Germany

Titan: An atmosphere not unlike Earth's billions of years ago

Enlarge Image
The Huygens space probe has sent back its first set of data about Saturn's largest moon, Titan, after landing successfully say space scientists.

The spacecraft probe had still been transmitting data for over two hours after it had landed they confirmed.

"We are the first visitors to Titan," said an excited Jean-Jacques Dordain, director general of the European Space Agency (Esa).

It is also the furthest from Earth a spacecraft has ever been landed.

"In the morning we had an engineering success and this afternoon we can also say we have a scientific success," he added.

Signal excitement

Scientists were excited when the probe first relayed a signal to say it had negotiated Titan's atmosphere, and announced that the mission was a "success".

"I want to make sure that we don't miss the significance of seeing that signal," said Alphonso Diaz, associate administrator for science at the US space agency (Nasa).

See how the Huygens probe descended to Titan

Huygens is transmitting scientific data to its mothership Cassini, which is orbiting in space, for onward transmission to Earth.

We're doing something today which will last for centuries
Professor David Southwood, Esa
The orbiter turned towards our planet and sent the first packets of information.

These were received by the European space operations centre in Darmstadt, Germany, ready for scientific analysis.

The first signal from Huygens was picked up by radio telescopes in West Virginia, US between 1020 and 1025 GMT on Friday.

This told them that the pilot parachute had pulled off the probe's rear cover, allowing its antenna to start transmitting, and that its instruments were working.

When the European-built probe entered Titan's atmosphere at an altitude of 1,270km (789 miles) from the surface, it was travelling at over Mach 20 which is 20 times the speed of sound.

Once friction slowed the probe's descent to about Mach 1.5, it deployed the first of three parachutes, pulling off the rear cover that protected Huygens from the fierce heat as it entered the atmosphere.

"We're doing something today which will last for centuries," said Professor Southwood,

"You have to take risks, otherwise, nothing ventured, nothing gained."

Unknown surface

Titan is veiled by a thick orange haze which obscures its surface features. Huygens could have land with a thud on ice and rock, squelched into tar-like gunge, or splashed down in an oily sea.

Impression of the Huygens probe landing on Titan
1. HASI - measures physical and electrical properties of Titan's atmosphere
2. GCMS - identifies and measures chemical species abundant in moon's 'air'
3. ACP - draws in and analyses atmospheric aerosol particles
4. DISR - images descent and investigates light levels
5. DWE - studies direction and strength of Titan's winds
6. SSP - determines physical properties of moon's surface

Hopes ride on Huygens
Huygens probe 'looks good'
Cassini's goodbye Huygens snap
The spacecraft should have taken about 750 images during its two-and-a-half-hour descent, shedding light on this cosmic enigma.

"This should provide a spectacular new view of Titan and hopefully a much greater understanding of this mysterious world," said Marty Tomasko, principal investigator on the Descent Imager/Spactral Radiometer instrument on Huygens.

Professor John Zarnecki, principal investigator on the surface science package on Huygens, has made no secret of his wish to land on an extraterrestrial ocean.

"I'm pleased that my instrument has got something to measure a liquid surface, a solid surface and something in between," he told the BBC News website.

"Despite the flybys of Titan by Cassini we still don't know [what its surface is like]."

Data gathered by the spacecraft should give detailed information on the moon's weather and chemistry.

The sounds of Titan's stormy atmosphere will be recorded with an onboard microphone, and scientists hope that they will even hear lightning strikes.

Dominated by nitrogen, methane and other organic (carbon-based) molecules, conditions on Titan are believed to resemble those on Earth 4.6 billion years ago.

As such, it may tell scientists more about the kind of chemical reactions that set the scene for the emergence of life on Earth.

Huygens has spent the past seven years tethered to the Cassini spacecraft, which arrived at Saturn in July 2004.

It had been coasting silently towards the exotic world for 20 days after being released from its mothership Cassini on 25 December.


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