The European Space Agency’s Philae lander weighed less than a sheet of A4 paper in the micro-gravity of Comet 67/P Churyumov-Gerasimenko when it drifted on to the comet’s surface this morning.
The control centre at Darmstadt in Germany had a collective seizure when the 10-year journey briefly went radio silent at the end of its seven hour descent phase from the Rosetta mother ship.
Then the signal came back, after what might have been a gentle bounce according to early analysis of the interrupted telemetry, and grown men and women wept and cheered as history was made.
Philae — think of a large box weighing 100 kgs on Earth dropping slower than a feather — fell 20 kilometres to the underside of one of the slowly rotating ends of what is a roughly dumbbell shaped comet nucleus that would fit, rather untidily, inside the Melbourne CBD.
What it met was so soft yet spongy that the harpoons that were supposed to help tether it to the surface didn’t fire, and Philae came to rest so lightly on the surface that screwing it down into position without sending it spinning off into space is one of the urgent priorities in the next day or so.
The above photo from Philae is the last released by ESA during the descent phase when it was 3000 metres above the underside of one end of the comet. One end of the comet can be seen in the background, mostly eclipsed by the nearer end.
The first panoramic images from Philae are expected later today, after breakfast local time, when we can expect a full-blown press conference.
Critical issues that remain to be clarified — apart from keeping Philae on the comet while it harpoons, screws and then digs into its microgravity surface — include the state of its solar panels.
They have to be correctly oriented to recharge the 64 hours or so of battery power it began using as soon as it was ejected from Rosetta .
In case this doesn’t happen, Philae is programmed to conduct two and a half Earth days of crammed studies of the materials on (and just under) the comet’s surface, instead of the potential six weeks of observations under solar power.
The science reporting of the landing has so far included some cringe-worthy references to the incredible speed of the comet. The comet is doing 18 kms a second in its orbit, but Earth averages 30 kms a second, so the fixation on speed, while relevant to the delicately calculated long voyage to Churyumov-Gerasimenko, has no relevance to the slow-motion events of today.
Similarly, references to the mission discovering the origins of (variously) human life, the water source for the world’s oceans, and the origins of the solar system, are embarrassingly gauche, and have been recited for almost every space mission ever sent to the moon, to Mars, Venus, Jupiter, Saturn, Titan, and the currently-in-progress journeys by NASA probes to Ceres and Pluto.
Rosetta and its Philae lander seek knowledge, which is what science does, rather than confirmation of informed guesses. If space has taught us one thing, it is that out there, everything we thought we once knew is wrong.