Nov. 6 is definitely a date that will go down in our history books. Ten years of speculations and calculations finally became reality when Rosetta successfully landed its probe, Philae, onto the Comet 67P/Churyumov-Gerasimenko.
Rosetta draws inspiration from its namesake the Rosetta Stone, a decree stone that played a pivotal role in aiding modern understanding of Egyptian hieroglyphs. The spaceship was commissioned by the European Space Agency (ESA) to allow scientists to learn more about comets and hopefully other parts of our solar system and universe. This probe landing on a comet some 510 million kilometers away marks a milestone in our space exploration efforts, as it is the first time such a feat has been accomplished.
Not many may be aware of this, but our very own Paul D. Feldman, a professor in the Hopkins Department of Physics and Astronomy, is a part of the Rosetta mission. Though not directly connected to the Philae part of the operation, he is very much involved with analyzing the ultraviolet spectrograms released from the comet’s atmosphere. According to Feldman, the 67P comet was not actually our first try at trying to land a probe.
“Since comets don’t have their own gravitational force, it really is difficult to predict the exact moment to launch the probe,” he said.
In order to get the best data about the surface and materials from the comet, scientists determined the location before the landing of the probe through a survey of the area by the Rosetta, from about 10 kilometers above the surface. Getting the Rosetta orbiter to accurately land the probe onto this still-orbiting comet with its varying trajectory is something that required years of meticulous planning and calculations. Radio signals take 20 minutes to travel up to the space probe, thus requiring precise planning right up to the last second before launching the probe. Even with all the preparation, due to the lack of gravitational force, Philae bounced twice before actually settling down on the comet.
With the probe on the comet surface, we now have access to all sorts of detailed information about the atmosphere of that space environment. Scientists have discovered that craters on the comet surface are caused by ice below the surface that vaporizes and fine dust material that covers it.
The texture, material and conductivity of the surface can be studied through samples collected and analyzed with labs based on the comet itself. Signals from the probe also deliver deeper insight into the diameter and size of the comet. Data on jets of gas and dust emitted allow scientists to relate that information to features on the surface of the comet.
However, due to the particular site Philae landed at, there have been challenges to gathering data.
“Due to the constant movement of the comet that is orbitting around the sun, there is not sufficient sunlight to sustain the solar cells on the probe,” Feldman said.
The combination of this and the decreasing temperature is what put Philae in hibernation after 60 hours on the comet. Data and images beyond that time period are currently being obtained through gas samples collected by the Rosetta ship 30 kilometers above the comet.
Fresh from this triumph, how does ESA — and also NASA — plan to continue their endeavors in space exploration?
“The next step would probably be to land rovers onto the surface, to gather more comprehensive data from the elements that are present on the comet,” Feldman said.
Scientists are also looking toward the possibilities of studying other comets — perhaps some that are closer to the sun. Observations taken from close to the surface can then be tied to data collected further away from orbiting satellites.
Chemical reactions that occur closer to the sun, like the decomposition of molecules into atoms for example, could then be analyzed through the atmospheric gas samples collected. Closer proximity to the sun will lead to evaporation of surface materials, and this will allow scientists to better investigate the interior of comets.
