Dawn Comes to Ceres

This Friday is going to be an exciting day in space exploration!

I just got finished watching NASA’s JPL briefing on the status of the Dawn spacecraft mission, and I loved it! And as Bill Nye says: “When you’re in love, you want to tell the world!”

The Dawn spacecraft was launched in September 2007, and in 2011 it became the first spacecraft to orbit a body in the main asteroid belt: it spent over a year examining the giant asteroid Vesta, making wonderful observations about its surface features and geologic activity. Vesta is the second-largest object in the asteroid belt, but Dawn wasn’t quite satisfied with that.

On Friday, it will reach Ceres, the largest object in the asteroid belt, and earn two other unprecedented titles: the first spacecraft to orbit two different worlds, and the first spacecraft to reach and investigate a dwarf planet.

This image shows an artistic rendition of the Dawn spacecraft
with Vesta to the left and Ceres to the right.
From http://dawn.jpl.nasa.gov/multimedia/spacecraft.asp

If you follow astronomy at all, you’ve probably heard of dwarf planets. If you’re old enough, and enough of an astronomy fan, you might even still associate the term with the bitter feelings many felt when beloved Pluto was stripped of its planetary status and reclassified as a dwarf. A dwarf planet is an object that orbits the sun (as opposed to moons, which orbit other bodies such as planets), and has enough mass to have a round shape like a planet, but isn’t big enough to clear its orbit of neighbors like the planets have done.

So why am I so excited about the exploration of Ceres? Well, it’s largely the doing of Carol Raymond, deputy principal investigator of the Dawn mission: during the briefing, she referred to Ceres as a “fossil.” Just as a paleontologist might investigate the remnants of the earliest, primitive forms of life on Earth, the Dawn scientists are investigating the remnants of the earliest, primitive bodies in our solar system - that's where the mission got its name! Most of the planets started off as small protoplanets similar to Ceres, but Ceres just never developed those planetary characters. As Mrs. Raymond said: it’s an intact protoplanet, a relic of the ancient solar system!

What do we know about Ceres?
Discovered in 1801, Ceres was first considered a planet, then an asteroid, until scientists settled on the term dwarf planet. It’s the giant of the main asteroid belt, 600 miles across. Unlike other bodies like the Moon or Vesta, Ceres retains a lot of volatile elements like water, comparable to the icy moons of the outer planets. Examinations of Ceres – its shape, its density, and models of its formation – lead researchers to suspect the dwarf once had a subsurface ocean, now frozen as an inner layer of ice. One of Dawn’s main objectives is to investigate the surface for any features that might tell us more about what’s going on underneath.

And whenever you hear the term “subsurface ocean” you know the astrobiologists are interested. Much like Europa and Enceladus, Ceres might offer us some more insights into the possibilities of extraterrestrial life.

Of course, the most exciting aspects of Ceres are the most puzzling! Dawn has been taking pictures as it approaches the protoplanet, and these pictures have revealed highly reflective "bright spots" on Ceres’ surface, mysterious features unlike any other observed in our solar system. Hypotheses abound! Are these patches of ice? Reflective minerals? Cryovolcanoes? Carol Raymond says cryovolcanism is unlikely given the shape of the bright areas, but until we get a closer look, we don’t know what they are! Fortunately, that closer look is coming very soon.

This image of Ceres, taken by Dawn on Feb 19th from nearly
29,000 miles away, shows its intriguing and enigmatic bright spots.
From http://photojournal.jpl.nasa.gov/catalog/PIA19185

Dawn’s initial arrival at Ceres Friday morning will actually happen while the spacecraft is on the opposite side of the dwarf – the “dark side” – so we won’t start receiving signals until it emerges a month later, but then the data will start pouring in! Between now and June 2016, Dawn will investigate Ceres from four different orbits, the last of which will bring the spacecraft about 235 miles from the surface, about as close as the International Space Station is to Earth.

Dawn is armed with a number of scientific instruments, as well as innovative and efficient Ion Propulsion engines (the participants of the briefing couldn’t seem to contain their excitement about these engines!). With a relatively low total-mission cost under $500 million, Dawn is designed, as project manager Bob Mase put it, for big science on a small budget.

The timing of Dawn’s approach also offers a great opportunity. Just four months later, on July 14^th, the New Horizons spacecraft will fly by Pluto, offering new and exciting data on our favorite dwarf planet. At the briefing, Jim Green, Director of NASA's Planetary Science Division, excitedly announced that NASA will then immediately begin making comparisons. As Pluto is more than twice the size of Ceres, and a lot farther from the sun, there will be a lot to compare and contrast between these protoplanetary cousins. 

Bob Mase assures us that the spacecraft is in excellent condition, and its approach so far is flawless. We should receive confirmation of a successful arrival by Friday afternoon, and then look forward to a flood of new data coming to us by April, and continuing for the next year. The enthusiasm of Carol, Jim, and Bob at the conference was infectious, and I definitely caught the bug. I've never written up a blog post so fast in my life!

JPL Director Charles Elachi stated at the beginning of the briefing: “Every time we visit a new object, we are always surprised.”

I can’t wait to see what surprises Ceres has in store for us.

For images Dawn has already captured of Ceres, visit www.nasa.gov/dawn.

The briefing will be available to replay at www.ustream.tv/nasajpl2.