Space Probe Starts Ten-Year Comet Chase

The countdown has started for the first ever mission to land a space craft on a comet -- after an original launch scheduled for Thursday morning, it has now been postponed for a day.

But scientists eagerly following the take-off from the launch pad in Kourous, French Guiana, will have a much longer time to wait before they can begin their experiments on the comet's surface: Touchdown isn't due until November 2014.

With ten years in the making and a billion euros ($1.25 billion) invested in it, the unmanned orbiter Rosetta is without a doubt the most ambitious and costly exploration of a comet, the fiery galactic rocks some scientists believe brought life to Earth. For the European Space Agency it is a chance to make history and add another piece to the giant puzzle of life's origins.

"This is going to be the ultimate cometary mission," declared ESA's director of science, David Southwood. "It will underpin cometary science for the next decades."

And indeed it should, considering it will take at least 10 years before the orbiter actually arrives at its destination, the comet Churyumov-Gerasimenko, measured at 675 million kilometers (421 million miles) from Earth. Once it fires its thrusters and closes in on the target, though, scientists hope it will help unlock some of the secrets of the Solar System, much as its namesake the Rosetta stone lifted the veil on Egyptian hieroglyphs.

Setting up lab

To aid in uncovering the mystery, Rosetta will dispatch a tiny robot lab, Philae (named after an obelisk that contained a final clue to the Rosetta stone), to gently land on the surface of "C-G." But because gravity is so low on comets, Philae will fire a small tethered harpoon into the rock's surface to anchor itself and then drill down a few centimeters for a good hold.

"Landing is not so much of a problem," said Eduard Müller from the German Aerospace Centre (DLR) in Cologne, which is managing the landing phase of the ESA mission. "The real difficulty is keeping the lab on the surface once it's there," he told DW-WORLD.

If that succeeds, Philae will put its arsenal of instruments to work to analyze the chemical, mineralogical and radioactive composition of the comet's surface. It will relay the data back to the Rosetta orbiter, which in turn will transmit the information back to the control center in Europe. Instructions from Earth to Rosetta take up to fifty minutes to reach their destination, even at the speed of light, so the orbiter is equipped with "smart computers" and the "intelligence" to look after itself.

No room for error

In the course of its journey to Chruyumov-Gerasimenko -- named after the Soviet astronomers credited with its discovery -- Rosetta and Philae will circle the sun four times. The craft will need three close fly-bys of Earth and one of Mars in order to pick up speed, using the planetary gravitational pull as a "slingshot" to reach more than 100,000 kph (60,000 mph) and catch up with the comet.

By May or June of 2014, Rosetta will enter orbit around the comet and begin edging towards its target. Cameras mounted on the craft will map C-G in detail to assist scientists in selecting a suitable landing site on the barely four-kilometer surface (2.5 miles across).

The minutest error in navigation will send the pair hurtling out of the Solar System.

Unlocking the key to life?

It's a ten-year risk in the making, but if it succeeds, the mission could provide answers to how life began on Earth. Comets are the most primitive material left after the making of the Solar System some 4.6 billion years ago. They are barely touched by gravity and heat and are light in weight for their size. Some scientists believe they may contain volatile and complex carbon molecules.

It is these molecules that may have helped seed life on Earth, according to the "panspermia" theory, which suggests the Earth, while still in its infancy, was bombarded with comets and asteroids. Elements from these bodies could have reacted with the oceans to provide the building blocks for DNA. Jean-Pierre Bibring of France's National Centre for Space Studies told reporters the "mission has the potential to make spectacular discoveries about the origin of Earth and, perhaps, about the origin of life itself."

Not as difficult as a Mars mission

It will be ten and half years before Rosetta and Philae report back with their findings, and as ESA knows from past missions, much can go wrong in the meantime despite the best of planning.

At DLR and ESA, scientists and engineers understand they are in it for the long haul. For Müller, the next decade is not just a time to twiddle fingers and wait until the comet comes into view. "There are corrections to the trajectory every time the orbiter does a "swing-by" to gain speed," he explained. "We also have plans to take a closer look at the asteroid belt."

Although recent unmanned flights to Mars, such as ESA's attempt to land its Beagle 2 probe on the Red Planet in January, have had their problems, Müller said he was confident the Rosetta would succeed.

"It has it own particular challenges such as the length of the mission, and the swing-bys," Müller admitted, "but it won't be nearly as difficult as landing on Mars."