The Goldstone Solar System Radar, part of NASA’s Deep
Space Network, made these observations of the recently discovered 500-foot-wide
(150-meter-wide) asteroid 2024 MK, which made its closest approach — within
about 184,000 miles (295,000 kilometers) of Earth — on June 29.
NASA/JPL-Caltech
The Deep Space Network’s Goldstone
planetary radar had a busy few days observing asteroids 2024 MK and 2011 UL21
as they safely passed Earth.
Scientists at NASA’s Jet Propulsion
Laboratory in Southern California recently tracked two asteroids as they flew
by our planet. One turned out to have a little moon orbiting it, while the
other had been discovered only 13 days before its closest approach to Earth.
There was no risk of either near-Earth object impacting our planet, but the
radar observations taken during these two close approaches will provide
valuable practice for planetary defense, as well as information about their
sizes, orbits, rotation, surface details, and clues as to their composition and
formation.
These seven radar observations by the Deep Space
Network’s Goldstone Solar System Radar shows the mile-wide asteroid 2011 UL21
during its June 27 close approach with Earth from about 4 million miles away.
The asteroid and its small moon (a bright dot at the bottom of the image) are
circled in white.
NASA/JPL-Caltech
Passing Earth on June 27 at a distance
of 4.1 million miles (6.6 million kilometers), or about 17 times the distance
between the Moon and Earth, the asteroid 2011 UL21 was discovered in 2011 by
the NASA-funded Catalina Sky Survey, in Tucson, Arizona. But this is the first
time it has come close enough to Earth to be imaged by radar. While the nearly
mile-wide (1.5-kilometer-wide) object is classified as being potentially
hazardous, calculations of its future orbits show that it won’t pose a threat
to our planet for the foreseeable future.
Using the Deep Space Network’s 230-foot-wide
(70-meter) Goldstone Solar System Radar,
called Deep Space Station 14 (DSS-14), near Barstow, California, JPL scientists
transmitted radio waves to the asteroid and received the reflected signals by
the same antenna. In addition to determining the asteroid is roughly spherical,
they discovered that it’s a binary system: A smaller asteroid, or moonlet,
orbits it from a distance of about 1.9 miles (3 kilometers).
Because close approaches by asteroids the size of 2024
MK are relatively rare, JPL’s planetary radar team gathered as much information
about the near-Earth object as possible. This mosaic shows the spinning
asteroid in one-minute increments about 16 hours after its closest approach
with Earth.
NASA/JPL-Caltech
“It is thought that about two-thirds of asteroids of this size are binary
systems, and their discovery is particularly important because we can use
measurements of their relative positions to estimate their mutual orbits,
masses, and densities, which provide key information about how they may have
formed,” said Lance Benner, principal scientist at JPL who helped lead the
observations.
Second Close
Approach
Assembled into this animation, observations from
NASA’s Goldstone Solar System Radar show the tumbling asteroid 2024 MK shortly
after it made closest approach with our planet on June 29. The 150-meter-wide
asteroid’s orbit was slightly altered by Earth’s gravity as it passed.
NASA/JPL-Caltech
Two days later, on June 29, the same
team observed the asteroid 2024 MK pass our planet from a distance of only
184,000 miles (295,000 kilometers), or slightly more than three-quarters of the
distance between the Moon and Earth. About 500 feet (150 meters) wide, this
asteroid appears to be elongated and angular, with prominent flat and rounded
regions. For these observations, the scientists also used DSS-14 to transmit
radio waves to the object, but they used Goldstone’s 114-foot (34-meter) DSS-13
antenna to receive the signal that bounced off the asteroid and came back to
Earth. The result of this “bistatic” radar observation is a detailed image of
the asteroid’s surface, revealing concavities, ridges, and boulders about 30
feet (10 meters) wide.
Close approaches of near-Earth objects
the size of 2024 MK are relatively rare, occurring about every couple of
decades, on average, so the JPL team sought to gather as much data about the
object as possible. “This was an extraordinary opportunity to investigate the
physical properties and obtain detailed images of a near-Earth asteroid,” said
Benner.
The asteroid 2024 MK was first reported
on June 16 by the NASA-funded Asteroid Terrestrial-impact Last Alert System
(ATLAS) at Sutherland Observing Station in South Africa. Its orbit was changed
by Earth’s gravity as it passed by, reducing its 3.3-year orbital period around
the Sun by about 24 days. Although it is classified as a potentially hazardous
asteroid, calculations of its future motion show that it does not pose a threat
to our planet for the foreseeable future.
The Goldstone Solar System Radar Group
is supported by NASA’s Near-Earth Object Observations Program within the Planetary Defense Coordination Office at
the agency’s headquarters in Washington. Managed by JPL, the Deep Space Network
receives programmatic oversight from Space Communications and Navigation program office within the Space Operations Mission Directorate,
also at NASA Headquarters.
More information about planetary radar
and near-Earth objects can be found at:
https://www.jpl.nasa.gov/asteroid-watch
Source: NASA’s Planetary Radar Tracks Two Large Asteroid Close Approaches - NASA
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