PROJECT HERA - TRIPLE-HEADER ASTEROID PROBE WASHINGTON -- It's a candy sampler of a space
mission. You get a little taste of one asteroid to whet your appetite for a taste of others.Scientists are planning a $240 million grab-and-run mission at three
asteroids using a hovering spacecraft that will collect material at space rocks the way a hummingbird gathers pollen at flowers. The spacecraft then will rocket that asteroid material to Earth. "Doing this mission is just at our fingertips but it's within our grasp," said Derek Sears, a space scientist and chemistry professor at the University of Arkansas in Fayetteville.
Sears is team leader on the project named Hera, after the Greek goddess and mother of the three "graces" -- joyfulness, bloom and brightness.
"Only now has this mission become technically feasible. But even so, we're stretching every muscle," he told SPACE.com. Hera is to be proposed as a NASA
Discovery-class mission of the cheaper, better, faster variety.Get the drill?
While still on the drawing board, scientists already have selected three targets for Hera, all about 150 million miles (240 million kilometers) from Earth.
Liftoff is scheduled aboard a
Delta 2 rocket for January 2006. The spacecraft would first reach asteroid 1999 AO 10 seven months later and spend 99 days hovering above the space rock.After that, Hera will change course and fly to asteroid 2000 AG 6. It is to arrive there in November 2008 and stay for 98 days.
Then Hera will fly to
Asteroid 1989 UQ in March 2009 and stay there for 205 days.Finally, it will head back in the vicinity of Earth where it will jettison a small capsule into the atmosphere. That capsule will parachute to a landing on Earth in November 2010.
The above images display an example of the drill that will extend from the spacecraft, and then drill and capture samples of from the asteroid's surface.
During the nearly five-year trip, Hera would be making a literal "pit stop" at each of the asteroids.
Hovering above the asteroids, the probe would extend a high-speed drill into the asteroid's surface. Fragments from the drilling would be captured and stored in small chambers on the spacecraft, then transferred into sample-return canisters.
At least nine samples could be collected from the three asteroids.
"We're at a stage now where this is the next logical thing to do," Sears said.
Around in circles
Hera is feasible thanks largely to the legacy of other
spacecraft.It borrows from Deep Space 1, which uses ion engines for propulsion and automatic navigation software. Hera also uses technology from the
Stardust mission that is en route to snag and return comet dust from Wild 2. ~
Hera's planners also are incorporating knowledge gained from the Near Earth Asteroid Rendezvous (
NEAR) probe that is now orbiting asteroid Eros, about 74 million miles (118 million kilometers) from Earth.
Craters on Eros contain boulders of various sizes.
Bringing back the goods from various asteroids is essential to sorting out the true story about our solar system's early history, Sears said.
The amount and quality of science data produced by Hera could be higher than any mission since Apollo moonwalkers retrieved lunar samples in the 1960s and 1970s, Sears said.
To date, studying meteorites recovered here on Earth has given scientists "hands-on" clues as to what conditions existed when the solar system was formed some 4.5 billion years ago.
"But I think we've reached a point where we done as much as we can do. We're going around in circles in many respects," Sears said.
On-the-spot samples
Collecting on-the-spot asteroid samples is a preferred way to dig into the history of the solar system, said Clark Chapman, a scientist at Southwest Research Institute in Boulder, Colorado.
"Despite the fact that a few of my colleagues are optimistic that they know where meteorites come from, we really don't know," Chapman said. "We don't know what kind of body they're from."
The best way to answer that, he said, is to tote to Earth asteroid samples from a known source -- as Hera will do -- and then compare those samples with current data on meteorites.
"Then, I think, there's great promise in actually telling, finally, a coherent story," Chapman said.
Linking the various types of Earth-recovered
meteorites to classes of asteroids remains a head-scratching exercise, Chapman said."The chief reason that progress has been inhibited, I think, is that we don't know where the meteorites come from," he said.
In that sense, Hera has "a huge role" to play in deciphering the mystery of asteroids, said mission scientist Donald Brownlee, an astronomer at the University of Washington in Seattle.
"We have asteroids and meteorites -- and cosmic dust of course -- but it is difficult to link the two to provide solar-system context," Brownlee said.
Just a bit
Hera would haul to the asteroids newly devised sampling technology.
"We call it the 'touch-and-go' sampler," said Stephen Gorevan, chairman of Honeybee Robotics, Inc. in New York City. "The key feature of this sampler is that no risky and expensive landing is required."
Once Hera floats into position over a select site, a flexible boom reaches out from the spacecraft. The boom, which can be stretched out nearly 5 feet (1.5 meters), is tipped with a spinning, counter-rotating bit that slices into the asteroid's surface.
The cutting head and temporary sample-storage chamber is retracted back into the spacecraft. The asteroid material is then transferred into a canister for return to Earth.
Depending on the type of asteroid material the drill runs into samples as deep as 1 to 3 feet (about 0.3 to 1 meter) might be collected.
Early tests of the drilling and sampling device have produced results "better than anticipated" Gorevan said.
High hopes
The NEAR spacecraft, which has orbited
Eros since February, boosts the probability of success for Hera, Sears said."Getting
NEAR closer and closer to the asteroid without destroying it sure helps us make our case for Hera," Sears said.There's a diversity of asteroids that range in composition from iron objects and volcanic-like rock to bits of small stone or gravel loosely clumped together.
"Asteroids range all over the map. That's why multiple sampling is key to the Hera mission," Sears said.
While there is much science behind Hera, knowing more about asteroids could also help protect Earth from future run-ins with falling space rocks.
"While the likelihood of impact is small, the effect is devastating. So there's the logic," Sears said.
"If you have some clue as to what these objects are made of, you'll also learn how best to deflect them from Earth," he said. "Also, you can estimate what's going to happen if they hit the Earth. A fluff ball hitting Earth is not quite the same as an iron object."
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