COMET 67P is having a breakout. In close-ups of its skin, the European Space Agency鈥檚 Rosetta probe has spotted ice patches and steaming pits, hinting at turmoil within.
Like other comets, 67P doesn鈥檛 reflect much sunlight 鈥� it鈥檚 blacker than coal. But the Rosetta team has seen shiny spots twinkling up from the surface that look like . The ice is peeking through gaps in a skin of dark dust.
But it鈥檚 67P鈥檚 newly discovered pits that are especially interesting. As Rosetta neared the comet, it saw circular holes. 鈥淚magine you took a steel rod and just punched it in the snow,鈥� says Carey Lisse of the Johns Hopkins University Applied Physics Laboratory in Maryland.
Advertisement
鈥淚magine you took a steel rod and just punched it in the snow 鈥� that鈥檚 like the pits found on Rosetta鈥�
Closer inspection revealed a flurry of activity. 鈥淲e were seeing tiny jets of gas and dust that were escaping from the pits,鈥� says Jean-Baptiste Vincent at the Max Planck Institute for Solar System Research in G枚ttingen, Germany.
The pits are too deep to be impact craters, and too big to have been excavated by the jets that spew from their walls. Instead, the team thinks they could be sinkholes where cavities inside the comet have been uncovered. 鈥淵ou have a ceiling over this cavity, and at some point the ceiling cannot support its own weight, and everything collapses,鈥� Vincent says.
After that cave-in, dust settles on the cavern floor. But the walls are left dust-free, letting sunlight shine on exposed ice 鈥� which powers the jets Rosetta saw ().
What鈥檚 unclear is how such underground cavities could exist in the first place. It鈥檚 possible they could have been packed with ice that vaporised and escaped through the surface, leaving a hole behind.
The fresh pits suggest that 67P hasn鈥檛 spent much time near the sun, which would have caused even more erosion, Vincent says. Comet watchers are keen to see what else Rosetta will uncover. 鈥淲e鈥檙e going to learn a lot more,鈥� says Lisse.
This article appeared in print under the headline 鈥淪inkholes and ice spotted in comet close-up鈥�
