Spacecraft puts scientist at dawn of solar system
Images from Dawn's framing cameras have revealed mysterious grooves or troughs across the middle of Vesta, an asteroid that UCLA space scientist Christopher Russell has waited 17 years to reach since he first proposed ths space expedition to NASA. To see a video of Vesta as it rotates, go here. Photos and video provided by NASA.
This promises to be a bountiful year of discovery for UCLA space scientist Christopher Russell and his team of some 80 scientists from planetary and astrophysical institutes and universities around the world.
Since July, an unconventionally propelled spacecraft named Dawn has been orbiting an asteroid after making a 1.7 billion-mile, four-year journey from Earth. Russell, a professor of geophysics and space physics and the chief science investigator of the ambitious Dawn Mission, has been waiting 17 years — since 1994 when he first proposed the project to NASA — to reach Vesta. The asteroid, researchers hope, will provide answers to some fundamental questions about how the Earth — and other planets — formed.
"I’ve been caught calling Vesta the smallest of the terrestrial planets," said Russell with a mischievous smile. "It’s not just a rock. It was an active body at one time, getting bigger, growing, trying to do the same things that the Earth does. But it didn’t have much gravity." Located in the main asteroid belt, it also didn’t fit comfortably into the International Astronomical Union’s definition of a planet.
The unknown story of what happened to and on Vesta — where, scientists believe, volcanoes once raged, lava flowed and craters formed, water once pooled and a cataclysmic collision with a huge object re-sculptured its surface — could come to light this or next year. Dawn’s highly advanced cameras, spectrometers, gamma ray detector and other instruments are reaping data from Vesta’s surface during precisely prescribed orbits that vary in altitude to give each instrument an optimal operational range.
By studying the asteroid’s craters and debris-strewn fields, mysterious dark spots and shadows, geological composition, and tectonics and topography, Russell and his team hope to learn more about processes that could provide insight about the evolution of planets like Earth.
Early images from Dawn look promising. "There’s so much more going on there than we ever expected," said Russell, who has been participating in space missions for more than four decades. "Before you get there, there’s always a little self-doubt. Did I really pick the right body to go to? Am I really making the right measurements? Is this the right thing to do?"
Those doubts dissolved with the tantalizing pictures Dawn began sending back to Earth last month, the first close-up images of this body ever seen by man.
"We didn’t just find a broken-up rock out there. What we found is really a very rich surface. It looked bumpy at first sight, but now we see grooves on the surface — we call them troughs. … Something slammed into it and severely compressed the surface. It pushed the land up, and then the land fell away, leaving these ridges in this area," he said, pointing to the strange troughs that seem to wrap around Vesta’s middle like a belt. "We think it’s sort of like the Rift Valley in Africa. But in this case, the rift was made by this strong impact that occurred in the south."
Next July, Dawn will tug itself free from Vesta’s gravitational pull by using its unique ion propulsion system — a technology that once only existed on the TV series, "Star Trek." The spacecraft will then set out on a three-year journey to an even farther object, the asteroid Ceres.
Timing is everything for this second phase, said Russell, who can foresee a natural temptation to continue exploring Vesta beyond its yearlong stay. But keeping on schedule will assure that Dawn is in the right alignment by July to reach Ceres, which, like Vesta, is revolving around the sun.
"We have to be careful not to linger at Vesta," Russell warned. "There’s a tendency if you’re a scientist to say to yourself, ‘Well, if I could take one just more measurement. … ’ So we guard against that."
After completing its initial survey orbit at nearly 1,700 miles above Vesta, Dawn is now dropping closer, to 830 miles as of Sept. 13, while the German-made framing cameras continue to help scientists map Vesta’s surface. For now, the researchers can only see clearly the southern region of the asteroid, lit by the sun. Its more-cratered north side will become visible as the planet changes its position relative to the sun.
The closer the spacecraft gets to Vesta, the more enlightened — and excited — the scientists will become. "Eventually, we will have very sophisticated knowledge of Vesta, but in the beginning, what we learn will be simple and then grow in complexity and deeper understanding," Russell said with certainty.
Scientists believe that Vesta’s collision with something big was so powerful that it knocked loose small pieces, some of which have landed on Earth. In fact, one out of every 20 meteorites that has fallen on Earth has come from this asteroid, according to the mineral "fingerprints" that have been found in the meteorites.
But the questions for scientists go beyond the impact. "We’re trying to study the smallest element of planethood," Russell said. "What is the smallest object that you would call a planet? And can we go back in history 4.6 billion years when Vesta was formed — before the Earth was formed — to learn how these small bodies worked back then?"
A steep slope on Vesta appears in a photo taken by Dawn's German-made framing cameras.
From his sixth-floor office at Slichter Hall, Russell manages the constant flow of information coming from the spacecraft's instruments as well as from the Jet Propulsion Laboratory in Pasadena, where the Dawn Mission is being run. He sends portions of the data to research team members who are in charge of specific instruments, as well as to interdisciplinary task groups that Russell has set up to address specific questions.
Waiting to analyze their share of this trove of data are scientists from the Max Planck Institute for Solar System Research in Germany, the National Institute for Astrophysics in Italy and the Planetary Science Institute in Tucson, Ariz., to name but a few in Russell’s collaborative group.
Being principal investigator in a mission the size of Dawn "is like being the chair of a large department about the size of chemistry or physics," said Russell, who selected each member, in part, for his or her ability to work together.
And all have a role in Dawn’s teaching mission. "Those 80 people are the professors and teaching assistants — and the ultimate student is the public," said Russell, who spends a lot of time talking to the media, leading press conferences, speaking at conferences and educating the general public, which has shown a huge hunger for more and more images. NASA, in fact, counts on Russell and his colleagues to provide an "image of the day" for its website
Just as teachers must carefully plan their lessons to guide students through four years of school, Russell said, "We’re doing exactly the same thing with Dawn. [This year] we get to a certain level of detail. But then next year, we’re going into more detail — presumably, we will know why those grooves are that deep and that far apart. We’ll have studied the geochemistry, and we’ll understand what that black material is — which totally took us by surprise."
Russell will continue teaching his graduate-level seminars while keeping the public up-to-date on Vesta and attending major planetary meetings in Europe and the U.S. where he and his co-investigators will deliver more than 50 papers on Vesta. He is also working on NASA’s Cassini Solstice Mission on Saturn — "which is taking data every day" — and the European Space Agency’s Venus Express mission. Yet another project bringing in data that Russell must analyze is NASA’s twin Solar Terrestrial Relations Observatories now studying our sun.
Given the demands of his schedule, email from colleagues sometimes goes unanswered, Russell admitted. He had to miss a family reunion this summer when Dawn was just arriving at Vesta. But he still fits in visits with his grandchildren — precious time that can’t wait until 2015, when the Dawn Mission is slated to end.
"We’re put on this planet and given a set of capabilities. You have your health, time and a certain amount of intellect," he said fatalistically. "Every so often, one or another of those assets is insufficient for the task at hand. On a project like this, time is the limiting factor. So you have to prioritize everything you do. You’re going to have to lose all sense of guilt, because certain things just aren’t going to be done."