A NASA spacecraft rammed an asteroid at blistering speed Monday in an
unprecedented dress rehearsal for the day a killer rock menaces Earth.
The galactic slam occurred at a harmless asteroid 7 million miles (11.3
million kilometers) away, with the spacecraft named Dart plowing into the
space rock at 14,000 mph (22,500 kph). Scientists expected the impact to
carve out a crater, hurl streams of rocks and dirt into space and, most
importantly, alter the asteroid’s orbit.
“We have impact!” Mission Control’s Elena Adams announced, jumping up and
down and thrusting her arms skyward.
Telescopes around the world and in space aimed at the same point in the sky
to capture the spectacle. Though the impact was immediately obvious — Dart’s
radio signal abruptly ceased — it will take as long as a couple of months to
determine how much the asteroid’s path was changed.
The $325 million mission was the first attempt to shift the position of an
asteroid or any other natural object in space.
“As far as we can tell, our first planetary defense test was a success,”
Adams later told a news conference, the room filling with applause. “I think
Earthlings should sleep better. Definitely, I will.”
NASA Administrator Bill Nelson reminded people earlier in the day via
Twitter that, “No, this is not a movie plot.” He added in a prerecorded
video: ”We’ve all seen it on movies like “Armageddon,” but the real-life
stakes are high.”
Monday’s target: a 525-foot (160-meter) asteroid named Dimorphos. It’s a
moonlet of Didymos, Greek for twin, a fast-spinning asteroid five times
bigger that flung off the material that formed the junior partner.
The pair have been orbiting the sun for eons without threatening Earth,
making them ideal save-the-world test candidates.
Launched last November, the vending machine-size Dart — short for Double
Asteroid Redirection Test — navigated to its target using new technology
developed by Johns Hopkins University’s Applied Physics Laboratory, the
spacecraft builder and mission manager.
Dart’s on-board camera, a key part of this smart navigation system, caught
sight of Dimorphos barely an hour before impact. “Woo hoo!” exclaimed Adams,
a mission systems engineer at Johns Hopkins.
With an image beaming back to Earth every second, Adams and other ground
controllers in Laurel, Maryland, watched with growing excitement as
Dimorphos loomed larger and larger in the field of view alongside its bigger
companion. Within minutes, Dimorphos was alone in the pictures; it looked
like a giant gray lemon, but with boulders and rubble on the surface. The
last image froze on the screen as the radio transmission ended.
Flight controllers cheered, hugged one another and exchanged high fives.
Their mission complete, the Dart team went straight into celebration mode.
There was little sorrow over the spacecraft’s demise.
“Normally, losing signal from a spacecraft is a very bad thing. But in this
case, it was the ideal outcome,” said NASA program scientist Tom Statler.
Johns Hopkins scientist Carolyn Ernst said the spacecraft was definitely
“kaput,” with remnants possibly in the fresh crater or cascading into space
with the asteroid’s ejected material.
Scientists insisted Dart would not shatter Dimorphos. The spacecraft packed
a scant 1,260 pounds (570 kilograms), compared with the asteroid’s 11
billion pounds (5 billion kilograms). But that should be plenty to shrink
its 11-hour, 55-minute orbit around Didymos.
The impact should pare 10 minutes off that. The anticipated orbital shift of
1% might not sound like much, scientists noted. But they stressed it would
amount to a significant change over years.
“Now is when the science starts,” said NASA’s Lori Glaze, planetary science
division director. “Now we’re going to see for real how effective we were.”
Planetary defense experts prefer nudging a threatening asteroid or comet out
of the way, given enough lead time, rather than blowing it up and creating
multiple pieces that could rain down on Earth. Multiple impactors might be
needed for big space rocks or a combination of impactors and so-called
gravity tractors, not-yet-invented devices that would use their own gravity
to pull an asteroid into a safer orbit.
“The dinosaurs didn’t have a space program to help them know what was
coming, but we do,” NASA’s senior climate adviser Katherine Calvin said,
referring to the mass extinction 66 million years ago believed to have been
caused by a major asteroid impact, volcanic eruptions or both.
The non-profit B612 Foundation, dedicated to protecting Earth from asteroid
strikes, has been pushing for impact tests like Dart since its founding by
astronauts and physicists 20 years ago. Monday’s feat aside, the world must
do a better job of identifying the countless space rocks lurking out there,
warned the foundation’s executive director, Ed Lu, a former astronaut.
Significantly less than half of the estimated 25,000 near-Earth objects in
the deadly 460-foot (140-meter) range have been discovered, according to
NASA. And fewer than 1% of the millions of smaller asteroids, capable of
widespread injuries, are known.
The Vera Rubin Observatory, nearing completion in Chile by the National
Science Foundation and U.S. Energy Department, promises to revolutionize the
field of asteroid discovery, Lu noted.
Finding and tracking asteroids, “That’s still the name of the game here.
That’s the thing that has to happen in order to protect the Earth,” he said.
Source: Link
Tags:
Space & Astrophysics