The mission is run by the European Space Agency which sent the Rosetta into space almost a decade ago. It is now about 500-million miles from the sun, preparing to rendezvous with a comet known as 67-P. Most of the instruments on board have been in a sort of hibernation since 2011, but the Rosetta was programmed to send a signal to Earth on Monday, so scientists can fire it back up for the rest of the mission.
Physicist Paul Doherty with San Francisco's Exploratorium is following the mission. Doherty believes "comets are really important to understand because they contain the primitive elements from which the solar system formed." This mission may even determine whether comets are responsible for bringing water to Earth.
If all goes as planned, the Rosetta will reach the comet by August and go into orbit. Then in November, it will launch a small landing craft called Philae with its own robotic laboratory on board. Doherty said the plan is "to drill into the comet and bring samples of the comet into the Philae spacecraft and really look at the chemistry and the physics of the come in place for the first time ever. "
Over the next year, the Rosetta spacecraft will continue to orbit the comet as it falls toward the sun. The Exploratorium is using an exhibit that drops chunks of dry ice into water to show how the comet is expected to behave as it falls.
Comets are full of different types of ice. As a comet moves toward the sun, the heat turns the ice into gas. "The gas comes pouring out in jets, and the jets act like rocket motors," according to Doherty. The jets propel the comet, just as they propel dry ice in the Exploratorium exhibit. Doherty says this is what causes comets to have tails created as they speed through dust and gas in space. The jets of gas also make some comets spin, creating a swirling pattern.
Scientists hope the Rosetta spacecraft's cameras will capture Comet 67-P doing all these things and others they don't even know about yet. Doherty said, "Every astronomer knows that comets are unpredictable. They general statement is: Comets are like cats. They both have tails and they do what they want."
Written and produced by Jennifer Olney