A hitchhiker’s guide to a comet

This past January, I wrote about the Rosetta spacecraft and its decade-long flight to catch up with the Comet 67P in (see “Comet hunter wakes up to hitch a ride,” Jan. 24, 2014). On the morning of Nov. 12, Comet 67P picked up a hitchhiker. A little probe — no bigger than a washing machine and weighing in at 250 pounds — launched from Rossetta, called Philae. It even looks like a washing machine, albeit one that’s covered in solar panels and has three spindly legs jutting out at right angles from its base.

Yet this little guy made history. No one has landed anything on a comet before, let alone a comet 317 million miles from earth — a tumbling lump of dirty ice and rock shaped like a squashed barbell, 3.1 miles long by 2.4 miles wide. From the black and white photos being beamed back to earth, this lump of ice and rock resembles a poorly mixed chunk of concrete more than a snowball.

This is all happening at speeds of more than 84,000 mph.

It takes a signal about 38 minutes to travel from the European Space Agency in Darmstadt, Germany to reach our intrepid duo in the darkness of space, one way. So flying Philea by remote is out. This little guy was programmed to land itself. It took seven hours for the tiny ship to reach its goal of landing on a comet.

That is where things took an interesting twist.

For starters, the harpoons failed to deploy, since the entire mass of the comet generates a very weak gravity field. The harpoons were needed to anchor little Philae to the surface to prevent it from being flung back into space. Then it turns out it landed not once, but three times, before coming to rest under some kind of a cliff. Talk about cliffhangers.

It gets better, sort of. Poor Philae’s final landing place at the base of an ice cliff is in shadow most of the time. Its batteries are charged up by those solar panels, so darkness is not its friend. ESA got it to lift and spin into a slightly better position.

But only just so. With time and power going against it, the plucky probe proceeded to drill into the surface and sent data from its samples to Rosetta, which was then beamed back to ESA mission control in Darmstadt, Germany.

Then the battery power began to fall to a dangerously low level. ESA sent a command for Philae to go into idle mode. In other words, they put it to sleep. The hope is that it will be reawakened when the prospects of solar power improve. And that’s when things really become interesting.

You see, right now that comet is sleeping, too. But as it gets closer to the sun it will wake up, as it’s surface begins to melt and boil out into space to form that glowing white nucleus and a tail that stretches back thousands of miles behind it. It is a sight that makes comets a wonder to look up at in the night sky.

In ancient times, comets were thought to be harbingers of evil times and death when a comet appeared. Today we know they are nothing of the sort. They could well have been the harbingers of life on this earth. That is what the mission is truly about. Comets could have the basic chemical ingredients of life deep within. There is a theory that in the early phases of the formation of the earth comets brought not only water but also seeded Earth with those chemicals from impacts on the surface of the young planet. Rosetta and Philae were sent there to find out if some of those theories could be fact.

Of course, an impact today would be a much different story. In 1908, the wilderness of Russia was rocked by what is believed to be an airburst of comet or cometary fragment. It flattened trees for miles, knocking the few residents living even farther out off their porches and shattering windows. It went off like a nuclear bomb, just without the radiation. If the same thing happened today, say in a major city, the results would be nothing short of catastrophic. Come to think of it, there were a pair of Hollywood blockbusters filmed along those story lines. Hmm.

Well, back to our story. Rosetta and little Philae will continue to ride it out with Comet 67P. The mission is just starting to become very interesting. I can’t wait for the next chapter to unfold in this decade-long saga. Science fiction is meeting science fact in the most extraordinary ways — and I’m loving every minute of it.

If this story intrigues you as much as it does me, here are some links to check it out in more detail.

Read more online at: bit.ly/1A9J51x, jpl.nasa.gov, or nasa.gov.

Wasilla resident Daniel D. Grota retired from the U.S. Army after more than 21 years of service.