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 19, 2014

Philae, the first robot probe to set down on the surface of a comet, detected molecules fundamental to the development of life on Earth in the thin atmosphere surrounding Comet Churyumov-Gerasimenko (67P). The molecules are “organics,” carbon-containing molecules that serve as the chemical building blocks of life as we know it. Philae landed on the comet on November 12 after a 10-year, 310-million-mile (500-million-kilometer) journey from Earth as part of the European Space Agency’s Rosetta mission.

Many scientists believe that life on Earth arose from organics that formed simple compounds, which then combined with one another to form the complex structures associated with living things. According to one theory, organic molecules or compounds may have arrived on Earth in meteorites or comets. Scientists have discovered several organic compounds in a number of carbon-rich meteorites called carbonaceous chondrites. In addition, organics were also among the samples collected and returned to Earth by the U.S. spacecraft Stardust from Comet Wild 2 in 2004.

The lander Philae (left) sits on the surface of Comet 67P in a photo taken by a camera on the Rosetta orbiter. (ESA/Rosetta/Philae/CIVA)

Philae, which is equipped with 10 scientific instruments, collected information for some 60 hours before mission scientists sent it into hibernation. The lander did not function as long as scientists had hoped because it landed in the shadow of a cliff, which blocked sunlight from its solar panels. While active, Philae also determined that the comet’s surface is covered by layer of dust 4 to 8 inches (10-20 centimeters) thick. Beneath the dust is very hard water ice. The ice is so hard that the lander’s drill had difficulty breaking through to collect a sample. Before it set down, Philae recorded the temperature on the comet’s surface as -243 °F (-153 °C). Rosetta scientists hope that as 67P and the orbiting Rosetta satellite make their way toward the sun, the solar batteries on Philae will recharge, allowing the lander to resume its on-site study of the comet.

Additional World Book articles:

• Comet (a Research Guide)
• Space exploration

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

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/

November 12, 2014

The European Space Agency (ESA) made space flight history today by deploying a landing craft to the surface of a comet. The Philae lander took only minutes after separating from its mother ship, the Rosetta spacecraft, to reach the nucleus (solid core) of Comet Churyumov-Gerasimenko. To prevent the lander from simply bouncing off the low-gravity comet into space, Philae immediately fired two harpoons into the surface. A small thruster also ignited to keep the lander grounded. However, scientists think the anchors that hold it to the surface failed to work properly, and they are investigating.

Rosetta, which was launched by the ESA in March 2004, traveled 3.7 billion miles (6 billion kilometers) through the solar system to meet up with comet 67P/Churyumov-Gerasimenko (nicknamed Chury). The probe used a series of fly-bys past Earth and Mars to increase its speed during the chase—Chury travels at a speed of around 34,000 miles (55,000 kilometers) per hour. During the lengthy journey, the probe was put into “hibernation” for for some 2.5 years to save energy.

The Rosetta spacecraft appears in a selfie with Comet 67P/Churyumov–Gerasimenko in October 2014, made using a camera on the Philae lander. At that point, Rosetta was about 10 miles (16 kilometers) from the surface of the comet. (ESA)

Scientists at the ESA’s flight center in Darmstadt, Germany, woke Rosetta in January 2014 for the last leg of its journey. In August, ESA scientists fired thrusters to maneuvered it into orbit around the comet. In August, Rosetta became the first spacecraft to rendezvous with a comet. (Other missions have rendezvoused with asteroids and meteors.) Once in orbit, Rosetta began to photograph and map the comet’s surface, mainly to choose a landing site for Philae. Rosetta will continue to study the comet as it orbits the sun.

Philae carries 10 instruments for studying Chury, including a drill to taking samples from below the surface. Scientists are particularly interested in learning about the chemical makeup of the comet and its structure. Comets are leftover debris from the formation of the solar system about 4.6 billion years ago. As such, their primitive material holds valuable clues about the formation of the planets and moons. The solar-powered lander Philae was expected to continue its investigations for at least a week.

More than 10 space missions have been launched to study comets. NASA’s Deep Impact spacecraft intentionally crashed an impactor into Comet Tempel 1 in 2005. In the mid-2000′s, the Stardust space probe collected and returned to Earth particles it captured by flying close to Comet Wild. However, until Rosetta, no mission had touched down on a comet.

Additional World Book articles:

• Comet (a Research Guide)
• Space exploration

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