Landing on a comet

Throughout human history, comets have been distant, mysterious heavenly bodies. The hunks of rock and ice streak through the sky, streaming bright tails of gas as the sun warms them.

On Wednesday, mankind finally made contact with one. The Rosetta spacecraft defied all odds and dropped its payload, a comet-sniffing probe named Philae, on a cold, speeding target more than 300 million miles from Earth.

Although scientists aren’t yet sure whether the probe will be able to anchor itself securely, for now its systems are operational and responsive. This comes as the climax of a decade-long mission. . . .

Landing a 220-pound probe on a 2.5-mile-wide comet is no small step for mankind. The comet hurtles around the sun at a speed of 84,000 miles per hour and doesn’t even have the decency to be smooth and evenly shaped, as comets so often appear to be in images.

Instead, the landing target is pitted and uneven, with the appearance of a child’s Play-Doh impression of a duck.

Tensions were high in the European Space Agency’s mission control room in Darmstadt, Germany, on Wednesday as the clock ticked closer to the proposed landing window. At 4 a.m. Eastern time, the team watched as Rosetta successfully ejected Philae, giving it a push toward the comet. Without thrusters or an engine, Philae simply dropped toward the piece of the comet that scientists thought it was most likely to successfully land on.

Then, a sigh of relief — Philae and Rosetta made satellite contact with each other. Without that connection, the probe would have been functionally lost.

With that final pre-landing checkpoint met, mission control hunkered down for seven hours of nerve-racking free fall, until Philae’s sensors finally confirmed a landing at 11:03 a.m. Eastern time.