June 18, 2015

Scientists were thrilled last weekend when the comet lander Philae awoke from a 7-month-long hibernation and contacted scientists on Earth. The lander is part of the Rosetta mission launched by the European Space Agency (ESA) to study comet 67P/Churyumov-Gerasimenko.

An artist’s illustration of Philae on Comet 67P/Churyumov-Gerasimenko. (Credit: DLR German Aerospace Center)

Rosetta is the first space probe to go into orbit around a comet. The ESA launched Rosetta on March 2, 2004, and it arrived at comet 67P in August 2014. Scientists believe that comets preserve dust, ice, and rock from the solar system’s formation. By closely studying the comet, they hope to learn more about the solar system’s makeup and history.

Rosetta carried instruments to study the comet from orbit, but it also carried a small lander named Philae. The lander touched down on the surface of the nucleus on Nov. 12, 2014. Philae was equipped with harpoons that should have anchored it to the comet’s surface. However, the landing failed to trigger the anchors, and the lander rebounded an estimated 0.6 mile (1 kilometer) above the comet’s surface. Philae returned to the comet and bounced one more time before settling in a heavily shaded area. Without sunlight on its solar panels, it could not recharge its batteries. Thus, the lander could only make observations and take readings for about 2 1/2 days before its batteries were depleted.

As 67P moved closer to the sun, more sunlight fell on Philae’s solar panels. The extra light gave the craft enough energy to contact Earth through the Rosetta orbiter on Sunday. The contact was brief, however—only 85 seconds long. ESA scientists are hoping contact can be sustained as the lander receives more energy from the sun.

Other World Book articles:

• Space exploration

• Space exploration (2014-a Back in time article)

November 14, 2014

Yesterday, the robot probe Philae began sending back the first images ever taken from the fractured terrain of a comet. After an awkward landing in which the probe bounced twice, initially back out into space, it stabilized on Comet 67P. It is currently attempting to drill into the surface of the comet. European Space Agency (ESA) scientists hope the tool will be able to capture some samples for analysis in Philae’s on-board laboratories.

An artist’s impression of the probe Philae (front view) on the surface of Comet 67P. (ESA/ATG medialab)

The objective of this ESA mission is to explore the origins of our solar system. Comets are believed to hold materials that are largely unchanged since the formation of the planets 4.6 billion years ago. Scientists speculate that comets delivered water to the early Earth. Others theorize that comets could even have “seeded” Earth with the chemicals needed to start life on the planet.

From the pictures Philae has returned to Earth, the ESA scientists believe it landed in the shadow of a cliff, meaning that the sunlight the probe receives is limited. As a result, its solar panels probably will not keep the battery systems properly charged, cutting short the run of the mission.

ESA’s Rosetta satellite, with its piggybacked Philae lander, was launched in 2004. The pair traveled 4 billion miles (6.4 billion kilometers) to reach Comet 67P, out near the orbit of Jupiter. After a long period of maneuvering into the correct position, Rosetta dropped Philae onto to Comet 67P on November 12.

Additional World Book articles:

• Comet (a Research Guide)
• Space exploration

For additional information about the Rosetta missions, see: http://rosetta.esa.int/