“It’s like shooting a bullet in the air with another bullet, with a blindfold on.” That’s how my genetics professor described the likelihood of landing a probe on a comet. But miraculously that’s what happened this very week! On November 12, 2014 the European Space Agency’s (ESA) Philae probe landed on a comet, marking this day as the first time the feat has been accomplished in human history.
According to the ESA’s website, this mission had been in the works for decades. So what made the endeavor so difficult? First of all, it was incredibly far away. It took ten years just to get to the area of the comet! The ESA reports that the instrument was launched in 2004 and has traveled 6.4 billion km through the solar system.
Comets are also moving at an incredibly high speed. Faster than the human mind can really comprehend. In an article for the New York Times, David H. Levy writes that comets while the Earth moves at an astounding 18 miles per second, most comets move much faster! (http://www.nytimes.com/books/first/l/levy-comets.html).
Finally, the comet wasn’t very big, which makes the feat even more impressive. This comet is likely only four km wide. In addition to these some other factors worth consideration are the gravity of the comet, its orbit, things that may pass the comet or fall in the path of the probe, chemical reactions taking place in space and heat. Even after reaching the comet, there is still the daunting task of launching the probe and landing it safely on the surface. So now imagine the calculations and understanding that had to go into hitting a target so small and far away, that is traveling on a path of its own, amidst a relatively unfamiliar world filled with complications. The trajectory of the Philae probe launcher and the descent of the probe itself had to be so exact and controlled to accomplish this task. And the amazing thing is that it was!
Source: http://www.esa.int/spaceinimages/Images/2014/02/Philae_touchdown
Since its landing, the batteries on the probe have died and it has gone into a “hibernation,” as ESA says in a report published yesterday (http://www.esa.int/Our_Activities/Space_Science/Rosetta/Pioneering_Phila…). But this is not to downgrade the success of the instrument. ESA reports that there was difficulty landing the probe at first. It bounced several times on the surface of the comet and landed in a shadow, causing difficulty in accessing the sun necessary to keep its solar-powered batteries charged. Scientists on the team also think that there just may not be enough sunlight reaching the comet at this time to recharge the batteries. However, “[the team] still hopes that at a later stage of the mission, perhaps when we are nearer to the Sun, that we might have enough solar illumination to wake up the lander and re-establish communication,” reported Stephen Ulamec, who headed the landing mission.
And it has already been successful. In it’s original announcement of the landing on November 12, the ESA outlines some tasks that the probe is meant to accomplish: “a full panoramic view of the landing site, including a section in 3D, high-resolution images of the surface immediately underneath the lander, on-the-spot analysis of the composition of the comet’s surface materials, and a drill that will take samples from a depth of 23 cm and feed them to an onboard laboratory for analysis” (http://www.esa.int/Our_Activities/Space_Science/Rosetta/Touchdown!_Rosetta_s_Philae_probe_lands_on_comet). The probe will also get information on electrical and chemical characteristics of the surface of the comet and, possibly, some internal readings. And though the probe is leached of battery power, it was able to successfully get all expected data for the initial part of the mission, reported ESA. Scientists will begin to analyze what they have.
Source: http://www.esa.int/spaceinimages/Images/2013/12/Philae_s_instruments_whi…
So why is this important for us? The comet that is now being analyzed is very old, and may have unique minerals or combinations of chemicals present. Because of this, it can give us a better understanding of other comets and planets throughout our solar system. “Rosetta [the mission’s name] is trying to answer the very big questions about the history of our Solar System,” said Matt Taylor, a scientist for the ESA. “What were the conditions like at its infancy and how did it evolve? What role did comets play in this evolution? How do comets work?”
The significance of the fact that this is a first cannot be ignored either. Because we don’t have information from other comets, this has opened up a world of space science that even scientists on the team may not completely understand at this point. The excitement about this event stems from the fact that we now have the opportunity to be just a bit more certain of the vast, confusing and largely undiscovered world around us.