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2010-04-17 03:23:57
Tariq Malik
SPACE.com Managing Editor
SPACE.com tariq Malik
space.com Managing Editor
space.com Fri Apr 16, 7:45 pm ET
President Barack Obama set a lofty next goal this week for Americans in space:
Visiting an asteroid by 2025. But reaching a space rock in a mere 15 years is a
daunting mission, and one that might also carry the ultimate safety of the
planet on its shoulders.
"It is probably the hardest thing we can do because the asteroid is not coming
on a schedule," NASA chief Charles Bolden told reporters late Thursday after
Obama announced his space vision.
And when a specific asteroid is eventually selected, the window to launch a
spaceship toward it will be much less forgiving than the windows for NASA space
shuttles bound for the International Space Station, Bolden said.
"The space station gives us five minutes," he explained. "I'm not sure what an
asteroid gives us, but then it doesn't come again for a lifetime."
And there's another compelling reason for touching an asteroid: Saving the
planet.
In a panel discussion that followed President Obama's Thursday space vision
speech, astrophysicist John Grunsfeld -- a former NASA astronaut who flew on
five shuttle missions -- suggested sending humans to purposely move an
asteroid, to nudge the space rock to change its trajectory. Such a feat, he
said, would show that humanity could deflect a space rock if one threatened to
crash into the planet.
"By going to a near-Earth object, an asteroid, and perhaps even modifying its
trajectory slightly, we would demonstrate a hallmark in human history," said
Grunsfeld, who flew on three shuttle missions to fix the Hubble Space
Telescope. "The first time humans showed that we can make better decisions than
the dinosaurs made 65 million years ago."
Take the moon, Grunsfeld said. Tycho crater, a huge impact crater on the moon
visible from Earth, was created when an asteroid crashed into it 95 million
years ago, he said.
"The dinosaurs saw that," Grunsfeld told reporters. "Thirty million years later
they're snuffed out when the same thing happens to the Earth." [Asteroids Up
Close.]
If humanity doesn't develop a capability to meet space rocks head-on, and win,
than it is almost a certainty that an asteroid will eventually threaten life on
Earth, he added.
TV's Bill Nye the Science Guy, vice president of the Planetary Society, said
the president's asteroid plan is carries risk, since it sends astronauts so far
from home. But it is risk worth taking.
"You're saving all of humankind," Nye said. "That's worthy, isn't it?"
What's out there
Scientists estimate there are about 100,000 asteroids and comets near Earth,
but only about 20,000 are expected to pose any risk of impact. NASA has found
about 7,000 of those objects, 1,000 of them flying in orbits that could
potentially threaten the Earth in the future, NASA scientists have said.
Astronomer Donald Yeomans, head of NASA's Near-Earth Object program office at
NASA's Jet Propulsion Laboratory in Pasadena, Calif., said there are about a
dozen near-Earth asteroids that could be within reach of manned spacecraft, but
most of those are relatively small. To make a crewed mission worth it, the
target space rock would likely have to be at least 300 feet (100 meters) wide.
For comparison, the space rock that exploded in a magnificent fireball over
Wisconsin this week was just 3 feet (1 meter) wide, Yeomans said.
"If you could study a few of them up-close, you get a better idea on how best
to deflect them," Yeomans told SPACE.com."
And more asteroids are being found all the time. NASA's WISE infrared space
telescope is discovering dozens of asteroids every day that were previously
unknown. New surveys and spacecraft will add to that space rock bounty over the
next 15 years to offer more candidates for a crewed asteroid mission, Yeomans
said.
New firsts in space
The bold new mission for NASA unveiled by President Obama Thursday was
ultimately aimed at sending humans to Mars in the mid-2030s. The asteroid
mission is just the first step.
"By 2025, we expect new spacecraft designed for long journeys to allow us to
begin the first-ever crewed missions beyond the moon into deep space," Obama
said. "We'll start we'll start by sending astronauts to an asteroid for the
first time in history."
Astronauts have been to the moon and it's time to do something new, Obama said.
He pledged to revive the Orion spacecraft, initially cancelled along the rest
of NASA's Constellation program building new rockets and spacecraft. Now it
will be used as a space station escape ship and, later, play role in deep space
missions, Obama said.
A mission to an asteroid would likely take months. Astronauts would rendezvous
with a space rock, not land on it because if its weak gravity, but NASA would
not send humans to asteroid to just look at it, Grunsfeld said.
"If you go up to this, you're going to want to crawl around on it and find out
what makes it tick," Grunsfeld said. Tethers or pitons would be required to
keep asteroid explorers from floating away, he added.
Astronauts on an asteroid mission would be flying outside the Earth's
protective magnetosphere, which shields the planet from harsh space and solar
radiation. Even the Apollo astronauts who landed and walked on the moon didn't
face such a risk.
"It's every bit as exciting in a different way, we're going to deep space. You
turn around and take a picture of the Earth, and it's going to be a dot. You're
not even going to see the atmosphere," Nye said. "Going to an asteroid, man,
it's tough and risky and dangerous, how cool is that?"
Space radiation and long-term isolation would be among the biggest challenges
for deep space missions, said MIT professor Edward Crawley, who participated in
the panel discussion with Grunsfeld and served on White House committee that
reviewed NASA's human spaceflight program.
Crawley recommended a tiered approach to training missions, with a series of
ever-longer expeditions preparing astronauts to the long treks to asteroids
and, eventually, Mars.
Understanding asteroids
In general, asteroids are no strangers to the people of Earth. Astronomers have
long-watched the space rocks from the ground while spacecraft have visited --
some even landed on -- asteroids in deep space.
Today, Japan's Hayabusa spacecraft is returning back from a huge asteroid
called Itokawa, where it attempted to collect samples to send back to Earth.
Hayabusa is due to return in June. Meanwhile, NASA's ion-powered Dawn
spacecraft is headed out to the asteroid belt to rendezvous with Vesta and
Ceres, the two biggest space rocks in the solar system.
But robots are only as good as their programming, and ultimately still rely on
human operators.
"Robots have never discovered things," Grunsfeld said. "People have discovered
things, using robots."
But there are secrets locked away on asteroids that may hold the key to
understanding the formation of the solar system. Asteroids are the thought to
be the leftover remnants of the solar system's buildings blocks. The organic
molecules and compounds on them may offer clues on how life began on Earth, and
if it's possible elsewhere in the universe, Nye and Grunsfeld said.
For Yeomans, who has studied asteroids for 40 years, hearing President Obama's
commitment to send humans to visit them was uplifting, to say the least.
"It was pretty exciting to hear him say that," Yeomans told SPACE.com. "Of
course, Congress still has to pass the budget, so all these things are up in
the air a bit."