Philae is stuck in a shadowy crater. Its battery is dying. What happens next?

[Buster's Uncle]

Philae is stuck in a shadowy crater. Its battery is dying. What happens next?
Vox
Updated by Joseph Stromberg on November 13, 2014, 4:30 p.m. ET@josephstrombergjoseph@vox.com



Wednesday morning, Philae became the first spacecraft ever to land on a comet.

However, we now know that it didn't go exactly as planned. The craft's harpoons failed to engage, so Philae ended up bouncing off the comet, then landing two hours later, a kilometer away from its intended landing site.

European Space Agency scientists now believe the lander is resting on its side, perhaps just inside the edge of a crater, with two of its three feet in contact with the comet. This certainly doesn't mean the mission is a failure, as Philae is still capable of gathering many types of data, such as photos, and transmitting them up to Rosetta.

 

A composite of six photos taken by Philae. (ESA)


However, the rocky landing does pose some difficulties for the mission going forward. Here's a recap of the current situation.


The bad news

Philae landed in the red area, and has bounced to somewhere within the blue area. (ESA)


The fact that Philae is resting on its side in a crater poses two big problems.

One is access to sunlight. The craft is equipped with solar panels, which are designed to top off its battery when the comet rotates to face the sun. In ideal conditions — such as on the relatively flat spot where Philae was supposed to land — this could have extended the craft's battery life significantly.

But currently, only one of the craft's two solar panels is getting any sunlight, and it's only getting about 90 minutes of light for every 12-hour period.

Without any solar power, Philae's battery was projected to empty about 64 hours after landing on the comet, which would mean late Saturday evening (EST). The slight amount of sunlight might extend this a bit, but the bottom line is that ESA scientists are now in a huge hurry to collect as much data before Philae shuts off.



This is how Philae should have landed — rather than coming to a rest on its side. (ESA)


The other problem is that Philae's instability means it probably won't be able to drill into the comet, extract a sample, and analyze it. The extremely weak force of gravity on the comet means that doing so could potentially send it back out to space, something the researchers say they're reluctant to risk. This was one of the most exciting scientific experiments of the mission, and it's looking like it may not happen.

This is also the reason that the researchers probably won't try to re-fire the harpoons or otherwise adjust the craft's position. Doing so could anchor it more stably or tip it upright, but it could also send it spinning out into space forever. And there simply isn't time to design and execute a plan that would minimize the risk of this happening.


The good news

The good news is that we've still put a spacecraft on a comet, and it can collect all sorts of data that will help us better understand comets than ever before.

Philae carries ten different scientific instruments, and eight of them have already sent back data. Apart from the drill, the craft has several cameras, an instrument that will send electromagnetic waves through the comet to analyze its interior, and sensors that measure the density and temperature of the comet's surface.



A diagram of Philae's instruments. CIVA and ROLIS are the cameras, MUPUS is the surface temperature sensor, and CONSERT is the radar-emitting device. (DLR)


The data these instruments have already sent back are unprecedented, and will be studied in the coming years to better understand the comet.

Further, as the battery life winds down, it's possible that scientists would activate the drilling system anyway, given that there won't be much to lose. If it successfully drills a sample without becoming unstable, Philae's other instruments will analyze the rock to determine its chemical content.

Additionally, scientists say that as the comet gradually nears the sun next year, it's possible the probe would be exposed to additional sunlight and wake back up, allowing for further investigations.

Finally, the key thing to remember is that the original plan called for 80 percent of the science of this mission to be carried out by the Rosetta orbiter, not the lander. Rosetta is capturing hundreds of amazingly detailed photos of the comet and analyzing the dust and gas given off by it as it vaporizes.



A photo of the comet's surface taken by Rosetta. (ESA/Rosetta/NAVCAM)


This is a big deal because the comet formed 4.6 billion years ago, from material leftover as Earth and the solar system's other planets were coalescing. As a result, understanding the composition of comets could help us better model the formation of the solar system.

Moreover, it's hypothesized that comets colliding with Earth during this era brought the water present on our planet today, and perhaps even organic molecules that gave rise to life. Learning more about this comet — and comets in general — might help us determine if this was true, providing a fascinating window into the history of all life on earth.


http://www.vox.com/2014/11/13/7214941/philae-comet-rosetta