Steve Hawley watched the news this week about the spacecraft landing on a comet with keen interest.
Hawley teaches astronomy at the University of Kansas, but before that, he flew in space shuttles five times for NASA. He deployed the Hubble Space Telescope, which made history-making discoveries about our universe. He was a big deal at NASA, one of its best explorers.
He says the comet landing is a big deal – and fun to watch.
The spacecraft lander, named Philae, has struggled to survive on the comet since it landed Wednesday, and may die soon if its solar panels fail to soak up enough energy to keep things going. But it’s already a success, having sent back some data and photos. Philae’s companion spacecraft, Rosetta, will continue to orbit the comet and send back more discoveries even if Philae dies.
Here are seven reasons Hawley told us why he’s so intrigued:
Why land on a comet? “The opportunity that is unique is to be able to explore what comets are made of.”
But from that, you can widen the vision to big discoveries, he said.
Origins of stars and life: “We know the earth was pummeled by comets four billion years ago; and we know from studying comets up to now that they contain a lot of water and ice. And we know, because of what we did with the (12-year NASA) Stardust mission – we got small pieces of comet dust, and learned that, besides water, there’s not only organic molecules, but complex organic molecules. So we know comets were an important early source of water – and organic molecules are the building blocks of life.”
Studying comets allows us to study the building blocks of the galaxy, and whether life is possible not only on Mars but everywhere, he said.
What comets are: “It’s about discovery. Comets represent the most primitive matter in our solar system – they are relics, the leftovers of what the solar system was originally made of.”
The speed of light: The comet, and the 220-pound Philae, are now 311 million miles from Earth. Even at the speed of light, that means the spacecraft’s Earth-bound commanders face a long delay in using electronic transmissions to tell the craft what to do.
“The sun is 93 million miles from Earth, and it takes light eight minutes to travel from the sun to us,” Hawley said. “So the time delay (in radio transmissions from Earth) would be something like half an hour.”
Challenges: It is really hard to remote-control land on a comet, he said. For one thing, the comet is traveling at 40,000 miles per hour, 311 million miles from Earth, so the physics of working out how to hit a 2.5 mile wide target are impressive. It took 10 years for the craft to reach its destination. And then came the rendezvous – landing on an unstable hunk of rock and ice that has not much gravity.
“It can be done, and we’ve demonstrated we are pretty good at it, but it’s hard. It was harder than with Hubble, because for one thing, we knew the Hubble orbit well. (Hawley not only deployed the Hubble telescope in a NASA space mission, but then flew on another mission years later to rendezvous and capture the Hubble for upgrades and repairs.)
Volatility: But the Hubble was, in comparison, a stable object. Comets are not stable at all.
“It is the nature of comets to have ice and volatile materials – volatile because they tend to evaporate, and when they evaporate, the escape of that material adds velocity. So the comet changes its orbit.”
Curiosity: Hawley’s space missions are years in the past, though he still sometimes gives commands to the Hubble, asking it to look at a system way out there that he’s still interested in.
But he said this comet mission, where he had no part, made him as happy and as curious as when he was an astronaut, or just a kid from Salina who looked at stars through lenses of dime store telescopes.
“Only now, we can actually get answers to a lot of those questions I had as a kid.”