Science and Society: Rosetta Space Mission

In early November, the Rosetta space mission will land on a comet. Arguably as momentous as putting a rover on Mars or a man on the Moon, this space expedition also gets my vote as the coolest to date.

I say this because the comet in question, 67P/Cheryumov-Gerasimenko, is moving 85,000 miles per hour and is almost a quarter of the size of Manhattan. Rosetta was launched in 2004 and took ten years to reach the comet. It followed an intricate trajectory that included four gravitational slingshots by Earth and Mars. The complexity and precision of the mission’s ballistics is mind-boggling, and makes me feel all the more insecure about my inability to accurately throw crumpled paper into a waste bin.

But the destination is more astounding than the journey. Astronomers describe comets as dirty snowballs composed of ice, dust, and rock hurling through space. They have a thin atmosphere and a characteristic, colorful tail because solar winds vaporize comet ice. Debris constantly breaks off from the comet and when the earth passes through a comet’s tail, the debris disburses in the atmosphere, causing a meteor shower. Comets are thought to originate from the Kuiper belt, a field of comets and asteroids just outside the orbit of Pluto, and from the Oort cloud, a surrounding jumble of icy objects that extends halfway to the nearest star.

Most exciting is that during the subsequent months after touchdown, the mission will relay data that will contribute to our understanding of the formation of the solar system and the origin of life.

Comets are thought to be among the most primitive objects in the solar system and leftover fragments from its formation. Rosetta project scientist Claudia Alexander explains, “Comets come from a distant place in space, and because of this we think they represent pristine, unchanged remnants of the distant past … comets present a unique ‘archeological dig’ opportunity.”

Rosetta rendezvoused with the comet in August and is currently orbiting and approaching it. In November it will be close enough to drop its lander, Philae, onto the comet. Philae is equipped with 11 instruments, and if all goes well it will start experimenting and sending back information.

Philae will analyze the structure, composition, thermal properties and outgassing of the comet. But the most interesting questions the mission explores are related to Earth.

The first is the origin of Earth’s water. One theory is that comets brought water to Earth. Analysis of the moon’s craters suggests that early in Earth’s history there was a chaotic period of frequent comet and asteroid impact. Most comets have a large amount of water, and it’s possible they supplied Earth with some or most of its water. One way for scientists to investigate this question is to measure comet water’s ratio of deuterium isotopes to common hydrogen. This ratio varies from location to location in the solar system, and will reveal whether or not the water on earth is similar to the water on comets.

Scientists also think comets and asteroids carry important chemicals for life such as nucleic and amino acids. Some scientists speculate that comets or asteroids could have seeded earth with these chemicals and contributed to the origin of life. Life on earth uses left-handed amino acid isomers, and by investigating the isomers of the comet’s amino acids we will discover whether left-handed or right-handed isomers are present on comets.

Rosetta is just one of several space missions planned for the near future. Equally exciting are the prospects of the replacement of the Hubble with the James Webb telescope, a robotic rover’s journey to the dwarf planet Ceres, and a manned expedition to Mars.

The moments of discovery when there’s a change in our perception of ourselves and our relationship to the universe are the most galvanizing aspects of science, and Rosetta is a perfect example. Rosetta hasn’t discovered anything yet and might not find anything of great significant. But it’s the intangible hope of future answers that inspires and motivates scientists to tirelessly confront the unknown. In general, this column will brood on issues in science that are more controversial, elicit greater trepidation and necessitate deeper nuance, but I wanted to start with an example of what, I think, most captivates people about science.