This imagery from NASA’s Hubble Space Telescope from Oct. 8, 2022, shows the debris blasted from the surface of Dimorphos 285 hours after the asteroid was intentionally impacted by NASA’s DART spacecraft on Sept. 26. The shape of that tail has changed over time. Scientists are continuing to study this material and how it moves in space, in order to better understand the asteroid. Credits: NASA/ESA/STScI/Hubble
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Analysis of data
obtained over the past two weeks by NASA’s Double
Asteroid Redirection Test (DART) investigation team shows the spacecraft's
kinetic impact with its target asteroid, Dimorphos, successfully altered the
asteroid’s orbit. This marks humanity’s first time purposely changing the
motion of a celestial object and the first full-scale demonstration of asteroid
deflection technology.
“All of us have a responsibility to protect our home planet. After all,
it’s the only one we have,” said NASA Administrator Bill Nelson. “This mission
shows that NASA is trying to be ready for whatever the universe throws at us.
NASA has proven we are serious as a defender of the planet. This is a watershed
moment for planetary defense and all of humanity, demonstrating commitment from
NASA's exceptional team and partners from around the world.”
Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit
its larger parent asteroid, Didymos. Since DART’s intentional collision with
Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to
measure how much that time has changed. Now, the investigation team has
confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32
minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes.
This measurement has a margin of uncertainty of approximately plus or minus 2
minutes.
Before its encounter, NASA had defined a minimum successful orbit period
change of Dimorphos as change of 73 seconds or more. This early data show DART
surpassed this minimum benchmark by more than 25 times.
“This result is one important step toward understanding the full effect of
DART’s impact with its target asteroid” said Lori Glaze, director of NASA’s
Planetary Science Division at NASA Headquarters in Washington. “As new data
come in each day, astronomers will be able to better assess whether, and how, a
mission like DART could be used in the future to help protect Earth from a
collision with an asteroid if we ever discover one headed our way.”
The investigation team is still acquiring data with ground-based
observatories around the world – as well as with radar facilities at NASA Jet
Propulsion Laboratory’s Goldstone planetary radar in California and the
National Science Foundation’s Green Bank Observatory in West Virginia. They are
updating the period measurement with frequent observations to improve its
precision.
Focus now is shifting toward measuring the efficiency of momentum transfer
from DART’s roughly 14,000-mile (22,530-kilometer) per hour collision with its
target. This includes further analysis of the "ejecta” – the many tons of
asteroidal rock displaced and launched into space by the impact. The recoil
from this blast of debris substantially enhanced DART’s push against Dimorphos
– a little like a jet of air streaming out of a balloon sends the balloon in
the opposite direction.
To successfully understand the effect of the recoil from the ejecta, more
information on of the asteroid’s physical properties, such as the
characteristics of its surface, and how strong or weak it is, is needed. These
issues are still being investigated.
“DART has given us some fascinating data about both asteroid properties and
the effectiveness of a kinetic impactor as a planetary defense technology,”
said Nancy Chabot, the DART coordination lead from the Johns Hopkins Applied
Physics Laboratory (APL) in Laurel, Maryland. “The DART team is continuing to
work on this rich dataset to fully understand this first planetary defense test
of asteroid deflection.”
For this analysis, astronomers will continue to study imagery of Dimorphos
from DART’s terminal approach and from the Light Italian CubeSat for Imaging of
Asteroids (LICIACube), provided by the Italian Space Agency, to approximate the
asteroid’s mass and shape. Roughly four years from now, the European Space
Agency’s Hera project is also planned to conduct detailed surveys of both
Dimorphos and Didymos, with a particular focus on the crater left by DART’s
collision and a precise measurement of Dimorphos’ mass.
Johns Hopkins APL built and operated the DART spacecraft and manages the
DART mission for NASA's Planetary Defense Coordination Office as a project of
the agency's Planetary Missions Program Office. Telescopic facilities
contributing to the observations used by the DART team to determine this result
include: Goldstone, Green Bank Observatory, Swope Telescope at the Las Campanas
Observatory in Chile, the Danish Telescope at the La Silla Observatory in
Chile, and the Las Cumbres Observatory global telescope network facilities in
Chile and in South Africa.
Neither Dimorphos nor Didymos poses any hazard to Earth before or after DART’s controlled collision with Dimorphos.
For more information about the DART mission, visit: https://www.nasa.gov/dart
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