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 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/