What Happened When the Philae Probe Landed on a Comet?

On November 12, 2014, ESA’s Philae lander became the first spacecraft in history to touch down on a comet — but its anchoring harpoons failed to fire, causing it to bounce more than half a mile above the surface and drift freely for nearly two hours before coming to rest wedged sideways in a shadowed crack.

A Ten-Year Journey to Comet 67P

The Rosetta mission launched in March 2004 with one audacious goal: to rendezvous with Comet 67P/Churyumov–Gerasimenko and deploy a small lander to study it up close. Over the next decade, the spacecraft traveled approximately four billion miles, looping around the inner solar system multiple times to build up the speed needed to match the comet’s trajectory. When Rosetta finally caught up with 67P in August 2014, the mission entered its most critical phase: getting Philae safely to the surface.

The Harpoons That Never Fired

Philae separated from Rosetta on November 12, 2014, and descended for about seven hours before touching down on the comet’s surface. The moment of contact was simultaneously historic and catastrophic. The two harpoons designed to anchor the washing-machine-sized probe to the low-gravity surface both failed to deploy. The leading explanation is that the firing wires or explosive charges inside them had degraded somewhere during the decade-long voyage through deep space. Without that anchor — and without the comet’s gravity strong enough to hold it — Philae bounced.

It rose more than 0.6 miles above the surface and floated silently over the alien landscape for nearly two hours. A second, smaller bounce followed, and then Philae came to its final, unplanned resting place: wedged on its side in a shadowed crack in a region scientists later named Abydos.

Sixty Hours of Science, Then Silence

The landing site was a problem. With its solar panels tilted away from the Sun, Philae could only generate a fraction of the power it needed. The probe’s primary battery — with roughly 60 hours of charge — began draining immediately. The science team scrambled to conduct as many experiments as possible before the lights went out. Philae managed to drill into the surface, analyze gas samples, and return a wealth of data before going permanently silent on November 15, 2014.

A Brief Resurrection

Seven months later, as Comet 67P swung closer to the Sun on its orbital path, sunlight began reaching Philae’s panels just enough to recharge them. On June 13, 2015, Philae woke up and made contact with Rosetta. Over the following weeks, it managed eight brief communication sessions before falling silent again — this time for good.

Rosetta Finds Philae — Weeks Before the End

For nearly two years, the exact location of Philae remained unknown. Then, on September 2, 2016 — just weeks before the Rosetta mission was deliberately ended by crashing the orbiter into the comet — Rosetta’s OSIRIS camera passed just 1.7 miles above the surface and captured it: a boxy shadow tucked into a crack, unmistakably Philae. The image confirmed what scientists had long suspected about its resting position, offering final closure to one of space exploration’s most dramatic stories.

What Rosetta Found in the Comet’s Coma

Beyond the lander saga, the Rosetta mission made a striking discovery: molecular oxygen (O₂) in the comet’s coma — the envelope of gas surrounding its nucleus. This was unexpected, as oxygen is highly reactive and rarely survives in space for long. One leading hypothesis holds that this oxygen was trapped inside the comet when it formed approximately 4.6 billion years ago, making it a preserved relic of the early solar system. Other researchers suggest the comet may be generating fresh oxygen at its surface through chemical reactions. Either way, the finding reshaped scientific thinking about comet chemistry and the conditions of the primordial solar system.