The Philae lander, which made history when it landed on Comet 67P in November, is long dead. But the orbiter that dropped it has only just begun its mission. On Thursday, the journal Science released a special issue highlighting the first scientific results from the Rosetta spacecraft.
“The story of the lander you already know, but that was only a small part of the mission,” said Dennis Bodewits, a University of Maryland astronomer who works on Rosetta’s Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS). Bodewits co-authored three of the seven papers on Comet 67P in this week’s Science.
Rosetta has continued to orbit the comet since Philae’s landing, and will keep doing so for about another year – long enough to follow the comet as it passes right by the sun. That’s going to be an exciting time for the mission scientists, because the comet, which is essentially a ball of ice covered in a layer of dust, should release more and more gasses as it heats up. The molecules inside its icy form have remained untouched since the early days of the solar system. Comets are considered a kind of cosmic time-capsule, but they don't last forever. Their ice slowly sublimes into gas over time.
"Comets start evolving faster and faster as they get closer to the sun," Bodewits said. Comet 67P won't evolve in the biological sense, but it's going to start spewing more and more of those ancient molecules as it approaches the heat of the sun. That gives scientists from NASA and the European Space Agency an even better chance of learning something about how the comets and planets of our solar system were born.
One of the first papers about the comet focuses on its unusual shape.
"Based on the light it reflects, we had an idea of what it would look like before we got there," Bodewits said. "But when we saw the pictures, it was nothing like we expected. It was quite strange."
Bodewits refers, of course, to the odd "rubber duck" shape of the comet. It almost looks like someone stuck two pieces of something together. And according to the new research, most of the jets of gas and debris the comet gives off seem to be at the duck's neck.
"That raises the question of whether it was formed this way from two different parts or whether it eroded into this shape," Bodewits added.
The researchers have also described the surface of the comet in detail, naming 19 distinct regions after ancient Egyptian deities. They hope to learn more in the future about where the comet, which is covered in a thick layer of dust, has the largest deposits of frozen and liquid water.
Another paper analyzes the "coma," of the comet -- the dust cloud that surrounds its body. As the comet approaches the sun and heats up, the coma will expand as the body loses mass. Bodewits and his colleagues hope that watching this process will reveal something about the evolution (and lifetime) of a typical comet.
The researchers also confirm that the comet is rich with organic molecules and lively with activity.
"We were surprised by how much activity we saw on the comet," Bodewits said of the jets of gasses and debris. "It looks almost like some of the comets we've observed before, much closer to the sun." But at the distance from our star that scientists first started observing 67P, it wasn't warm enough for heat to release all of those gasses from the ice.
In other words, the comet is already alive and kicking -- and scientists are on the edge of their seats waiting for its solar approach.