Comet hunter wake ups to hitch a ride

Since it’s launch in 2004, the Rosetta spacecraft has been bouncing around like a Newtonian billiard ball between Earth, Mars, the Sun and the asteroid belt. Now why was it doing this? Well, if you are trying to link up with a comet traveling at 40,000 km/h — or try 28,854 mph for those like me stuck in the old system — a direct flight is next to impossible.

Rosetta started its decade-long trek February 2004 aboard an Ariane-5 rocket, launched by the European Space Agency. Its target is the comet 67P/Churyumov-Gerasimenko, a weirdly shaped ball of ice, frozen gases and maybe some rock as well. It is about 4 km or 2.4 miles in diameter. It also has a short orbital period of 6.45 years, ideal for a spacecraft from Earth to be sent to.

The hard thing is it couldn’t be a direct flight. Instead, a celestial ballet that used gravity assists from our own Earth, Sun and Mars with endless orbits around all three in order to gain speed and to time it all for a rendezvous with Comet 67P years down range. It took some fantastic pictures of the Earth and Mars along with a couple of asteroids during this time. After a while, it went to sleep (so to speak) to conserve its energy for about two years. Its mission is a special one, one no one has tried before — and boy I admit it is a doozey.

The mission in general is for Rosetta to park itself in a low orbit around Comet 67P and detach a small lander to its surface, which will use a harpoon device to anchor itself to the icy object. Then the cool part kicks in. Both will hitch a ride toward the Sun. A Nantucket sleigh ride amongst the stars. Well, at least the lander will; Rosetta will orbit it. Whether or not either one or both survive the journey is part of the adventure.

The link up and landing will take place this May and the flight inbound towards the Sun will take months. The changes both craft will record should be astounding. Right now it is just a dirty snowball in the cold depths of space. But as it gets closer to our Sun, its surface will begin to out gas and boil off. Leaving a trail of dust, ice and whatever else it’s made of to spread out behind it in a tail that will stretch for thousands of miles by the solar wind. Then after it swings around the star, it will plunge back in the cold void. Its tail will fade to nothing and the comet will return back into a cold frozen state.

During this time both craft will take measure of it all. Rosetta will map its surface and take samples of all the materials ejected from the comet. Philae the tiny lander, will take drill samples to find out what is made of. Both will scratch, sniff and even take the comet’s temperature, all of which to be beamed back to the ESA and NASA. What a ride it will be!

Now why all this fuss over a comet? Comets are believed to be leftovers from the birth of our solar system. Ice bound time capsules of the beginning. Dirty snowballs of varying sizes from the size of an office building to many miles long. It is hoped to be found within them the very ingredients of life. There are theories going around in the world of science that billions of years ago, comets were essential to bringing water and life to a very special planet: Earth. Maybe Mars and the other planets with their moons as well. As far as we know, only life on this planet has been successful.

Most comets linger at the outreaches of the solar system in a region called the Ort Cloud. From time to time, one gets nudged out to fall toward the sun, a journey that takes centuries. Some get caught into a new orbit this way like Halley’s Comet, which reappears every 76 years. That comet has been seen for hundreds of years like clockwork since 1705. Each time one passes close to the sun they bleed off more and more of their surface, shrinking down to nothing in time.

Rosetta’s mission is to discover just what a comet is made of and what happens as it passes close to the sun on its ride with Comet 67P. On Jan. 20, the sleeping machine awakened after a long two-year sleep 500 million miles from the sun. Just past the orbit of the gas giant Jupiter, Rosetta beamed a signal and within it a bunch of tweets to Earth. The signal at the speed of light took over 45 minutes to reach the anxious crew at the ESA in Darmstadt, Germany. In 23 languages, its tweets simply said, “Hello World!” The fun is about to begin. I can’t wait for it to start.

If you want to find out more about Rosetta and it’s mission, here are some links:

• http://www.esa.int/ESA

• http://science.nasa.gov/missions/rosetta/

• https://rosetta.jpl.nasa.gov/

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