ExoMars 2016 begins 300 million-mile mission to search for life on Red Planet
Europe's greatest interplanetary adventure, the search for life on Mars, has taken off with the launch of a spacecraft programmed to sniff out methane around the Red Planet.
A Russian heavy-lift Proton rocket carrying the Trace Gas Orbiter (TGO) blasted off from the Baikonur Cosmodrome, Kazakhstan, at 9.31am UK time.
Also housed in the rocket's Breeze-M upper stage was a robot lander, Schiaparelli, which is due to parachute down onto a Martian plain in October.
Despite the text book perfect launch, scientists are not celebrating yet. The signal telling them that the spacecraft have safely set off on their seven-month 300 million-mile journey to Mars will not come until 9.28pm tonight, UK time.
ExoMars 2016 is the first phase of an historic 1.2 billion euro (£924 million) joint European-Russian mission to search for biochemical "fingerprints" of past or present life high above Mars and on its surface.
TGO is equipped with ultra-sensitive instruments for detecting trace gases in the Martian atmosphere, including methane which can be a sign of life.
On Earth, the gas is chiefly generated by billions of bacteria, many of which live in the guts of animals such as cows and termites. But it can also be released by volcanic activity and other geological processes.
The European Space Agency (ESA) orbiter will tell scientists whether Martian methane is most likely to have a geological or biological source.
Schiaparelli's main job is to test the descent and landing technology for ExoMars 2018, the next stage of the mission which is due to send a British-built rover to Mars in two years' time.
Fitted with a drill that can burrow 6ft (1.8m) into the Martian soil, the rover will search for evidence of long-dead or still living microbes underground.
The rocket upper stage, now in a "parking" orbit, is due to eject the TGO-Schiaparelli combination "stack" at 8.13pm UK time.
Travelling at 20,500mph (33,000kph), the spacecraft will then tear free from the Earth's gravitational field and begin their long coast through space to Mars.
Dr Manish Patel, from the Open University, who is in charge of TGO's ozone-mapping ultraviolet (UV) spectrometer instrument, watched the launch in a live link from the European Space Operations Centre (Esco) in Darmstadt, Germany.
He said: "It was a bit of a numbing few minutes before the launch... I won't be celebrating till we get final separation and the signal from the spacecraft telling us its on its way."
Scientists hope TGO will help them solve the mystery of methane on Mars.
Earth-based telescopes, the European Space Agency (ESA) Mars Express orbiter, and the American space agency Nasa's Curiosity rover have all detected traces of the gas around the planet.
But methane is quickly broken down by the sun's rays, and to persist in the atmosphere must be continually regenerated.
There are only two possible sources of Martian methane - ongoing geological processes such as volcanic activity, or life.
TGO's sensitive instruments will hunt for tiny traces of methane, study its carbon, and find clues pointing to its source.
Speaking from Darmstadt, Professor Mark McCaughrean, senior science adviser at the ESA and a former astrophysicist at the University of Exeter, said: " With the Trace Gas Orbiter we're going to go and study where the methane's coming from, study whether it's seasonal, study the geographical locations. And maybe, maybe, we can find out whether there is life, extant, on the Red Planet today."
The discovery of a likely source of biological methane on Mars would be a dramatic curtain-raiser for the ExoMars 2018 rover mission.
The six-wheeled rover, built by Airbus Defence and Space at its UK headquarters in Stevenage, will analyse samples drilled from the Martian soil for biochemical signatures of life, either left by long-dead microbes or organisms still thriving beneath the planet's radiation-baked surface.
Schiaparelli will pave the way for the rover mission by testing its Russian-designed descent and landing system, which involves aerobraking, parachute deployment, and retro rockets.
The 7.9ft (2.4m) diameter disc-shaped lander carries a small instrument package to take weather measurements, recording wind speed, humidity, pressure and the amount of dust in the air.
Airbus Defence and Space supplied the lander's heat shield, which has to withstand temperatures of up to 1,850C (3,362F) during its descent.
TGO and Schiaparelli are due to reach Mars on October 19, but will separate from each other three days earlier.
As TGO begins orbiting the planet, Schiaparelli - travelling at 13,000mph (20,920kph) - will enter the atmosphere and land on the Meridiani Planum plain close to the equator.
Scientists will have to wait a whole year for TGO to finish making orbital adjustments in preparation for its part in the mission.
From January 2017 to December the probe will use friction with the atmosphere to "aerobrake" and lower itself to an altitude of 250 miles (402km). Only then can its science operations begin.
The UK is the second largest contributor to ExoMars with a contribution of 205 million euro (£159 million) through the European Space Agency.
The mission has had a somewhat chequered history. Originally it was supposed to have been a partnership between ESA and Nasa, but the American space agency dropped out in 2012 because of budget cuts.
A year later, ESA signed a new deal with Roscosmos, which has now taken responsibility for landing the rover.