Rosetta’s Comet Revealing Earth’s Ancient Past

asteroid Rosetta’s comet in an image taken Dec. 10. The European Space Agency’s analysis of the space rock—and its water continent—continues through the ROSINA sensor partially developed at the ATC. (Image courtesy of ESA)

Taking detailed readings of space particles is hard enough, but try doing it while catching up to a comet traveling at over 40,000 mph.  That’s exactly what the ROSINA instrument on the European Space Agency’s (ESA) Rosetta spacecraft is doing, all to discover more about Earth’s origins by studying an icy rock hurtling through our solar system.

But it’s a special ice rock.

“This mission is important because it’s not just about studying a comet, which is itself an important task. It’s about the origins of our planet,” said Steve Petrinec, the ROSINA lead at Lockheed Martin Space Systems. “Comets are left over material from the formation of solar system. It’s like a time capsule of what Earth was made out of.  If we compare the materials in the comet versus what we have on Earth today, we learn so much more about how our world has transformed over time.”

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) consists of three sensors. Scientists and engineers at Lockheed Martin’s Advanced Technology Center (ATC) in Palo Alto, California helped develop one of them.  The double focusing mass spectrometer, or DFMS, measures neutral particles. Unlike other sensors on the mission that will land on the comet, this sensor resides on the orbiter spacecraft and focuses on measuring gases from the comet that become the atmosphere or coma.

Millions followed Rosetta and its comet—67P/Churyumov-Gerasimenko—last month as ESA landed the first spacecraft ever on a comet’s surface. They succeeded, though the final resting spot of Philae, the lander, was partially in the shade, reducing solar power and battery life. Its mission ended 57 hours after landing. However, the science mission continues because the Rosetta mother ship has more tools up her sleeve.

The ROSINA instrument has determined the composition of comet’s water vapor,finding it to be significantly different to that found on Earth. That means it is very unlikely that comets like 67P/Churyumov-Gerasimenko are responsible for the terrestrial water as some researchers predicted.

Scientists identify particles from the comet via their unique mass signature.

“DFMS has the highest mass resolution of any predecessor spectrometer used on a space mission,” Steve said. “This means that we are able to identify a wide variety of atomic and molecular species. We’re seeing exactly what particles are coming off that comet.”

It takes a lot of computing power to make sense of all the data. Steve said that ROSINA sends spectra samples of the comet—named Churyumov-Gerasimenko—every 20 seconds, or thousands of data files per day. The spacecraft’s sensors have been performing well since Rosetta “woke up” on January 20 after two and a half years of traveling dormant en route to its target.

ROSINA’s journey started long before launch in 2004. A team of scientists from the U.S., Belgium, France and Switzerland developed the advanced sensors throughout a decade of design and testing. The leader in this partnership was the University of Bern. The Swiss team designed DFMS and built its mechanical parts, the team from Belgium and France built the detectors, and the team from the U.S., including the University of Michigan, built the electronics and power delivery systems that enable the instrument and data flow to the instrument computer.

Overall, ROSINA’s data will fit in with the larger mission analysis—including the lander’s data—to give a complete picture of the comet’s composition.

ESA expects the mission to last through at least December 2015 so the spacecraft and lander can follow the comet to its closest point to the Sun—where it discharges the most material due to heating—and as it swings away.

“This kind of work is what the ATC is all about, creating first-of-class instruments that will further scientific discovery,” Steve said. “By working with an international team, we are helping reveal Earth’s origins to people all over the globe.”

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. ROLIS and CASSE were developed by the German Aerospace Center’s Institute of Planetary Research in Berlin. NASA's Jet Propulsion Laboratory, Pasadena, California, a Division of the California Institute of Technology in Pasadena, manages the U.S. contribution of the Rosetta mission for NASA's Science Mission Directorate in Washington.

Scientists believe Comet Churyumov-Gerasimenko, discovered in 1969, originated from the Kuiper Belt, a large reservoir of small icy bodies located just beyond Neptune.  It’s an active region where collisions are common and planets cause gravity changes, creating intersecting highways of rock where some objects get ejected out of the belt and head toward the Sun. This comet—at tall as Mt. Fuji—follows an orbit heavily influenced by another large body, Jupiter. It completes one orbit of the Sun every 6.45 years, and over its lifetime it has gradually gotten closer as it swings around the sun, but it has stabilized in recent decades.

December 17, 2014

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