Rosetta mission reports successful landing after nail-biting wait, but lander stability remains in question

Wednesday, November 12, 2014, 3:41 PM - Update 1:05 pm, Wednesday: The stability of the Philae lander is still unclear at this time.

Although the lander is, indeed, safely on the surface of Comet 67P/Churyumov-Gerasimenko, problems with the various equipment used during the landing procedure - rockets, harpoons and ice screws - are making the long-term stability of the lander a worrisome uncertainty.

It's going to take Philae mission controllers some time to understand how stable they are, but in meantime everything is working great. Yay!

— Emily Lakdawalla (@elakdawalla) November 12, 2014

Update at 12:00 pm Wednesday: After nearly 30 minutes of tension-filled waiting for word from the spacecraft and its lander, the ESA's Rosetta mission team now has a confirmed touchdown for Philae on the surface of Comet 67P/Churyumov-Gerasimenko!

After beaming across over 500 million kilometres of space to reach us here on Earth, signals from Rosetta finally arrived to beak the tension at ESA’s Space Operation Centre (ESOC) in Darmstadt, Germany, as they reported that the Philae lander had safely touched down on the surface of the comet.

TOUCHDOWN for @Philae2014! #CometLanding pic.twitter.com/ZMBeB8ng3h

— ESA Rosetta Mission (@ESA_Rosetta) November 12, 2014

Issues with the lander's rockets (designed to counter forces from Philae firing twin harpoons into the surface to anchor itself and pull itself down), as well as a slow spin detected in the lander as it descended towards the surface, both caused concerns as the team waited for word of success or failure ... a wait that, although was only around 28 minutes between actual touchdown to receiving word, still represented a decade's worth of waiting for everyone involved.

As the enthusiasm and celebrations in mission control calmed down some, and the details of the landing began to stream in, it was revealed that a few problems had, indeed, cropped up. As anticipated, Philae's rockets failed to fire upon its arrival at the surface, but mission controllers confirmed that the lander's harpoons also failed to fire. Since the rockets were only there to counter the force from the harpoons, that balanced things out in that respect, but it left the stability of the lander in question.

Update at 11:01 am Wednesday: One way or another, Rosetta's robotic lander, Philae, is now on the surface of Comet 67P/Churyumov-Gerasimenko. However, with concerns about technical problems and anomalies as the lander made its descent, the question now is - after a decade of planning and execution, will Philae survive to return the important scientific results the mission team has been hoping for all these years.

While tracking the Philae lander's descent over the past 7 hours, the ESA mission team has voiced concerns about the success of the maneuver.

Although the separation of the two craft went off without a hitch, initial comments from mission planners was that the small rockets on the top of the lander, which would propel it back to the surface after it fired its harpoons, may not function properly. While this is definitely a concern for the success of the landing, another issue that cropped up was an unexpected spin seen in Philae as the lander was making its descent.

How might the detected slow spin of @Philae2014 might affect the landing? It seems to have taken some of the team by surprise #cometlanding

— chrislintott (@chrislintott) November 12, 2014

Philae has three landing claws that are set to grasp the surface of the comet by driving screws in, but a spinning motion could add another, unwelcome complication to the maneuver.

One of the main concerns about the landing is that Philae could tip over. Mainly this possibility was attributed to something like a boulder or maybe uneven terrain, but a spin could cause the lander to lose its balance and fall over on its side.

EXTENDED ROSETTA MISSION COVERAGE: Check back throughout the day for more updates on this historic mission, and following along on Twitter, with the hashtag #CometLanding.