Near-earth asteroid might be a lost fragment of the moon

Date:
November 11, 2021
Source:
University of Arizona
Summary:
Near-Earth asteroid Kamo`oalewa could be a fragment of our moon.



FULL STORY ==========================================================================
A near-Earth asteroid named Kamo`oalewa could be a fragment of our moon, according to a new paper published in Nature Communications Earth and Environment by a team of astronomers led by the University of Arizona.


========================================================================== Kamo`oalewa is a quasi-satellite -- a subcategory of near-Earth asteroids
that orbit the sun but remain relatively close to Earth. Little
is known about these objects because they are faint and difficult
to observe. Kamo`oalewa was discovered by the PanSTARRS telescope in
Hawaii in 2016, and the name -- found in a Hawaiian creation chant --
alludes to an offspring that travels on its own. The asteroid is roughly
the size of a Ferris wheel -- between 150 and 190 feet in diameter --
and gets as close as about 9 million miles from Earth.

Due to its orbit, Kamo`oalewa can only be observed from Earth for a
few weeks every April. Its relatively small size means that it can
only be seen with one of the largest telescopes on Earth. Using the UArizona-managed Large Binocular Telescope on Mount Graham in southern
Arizona, a team of astronomers led by planetary sciences graduate student
Ben Sharkey found that Kamo`oalewa's pattern of reflected light, called
a spectrum, matches lunar rocks from NASA's Apollo missions, suggesting
it originated from the moon.

The team can't yet be sure how it may have broken loose. The reason,
in part, is because there are no other known asteroids with lunar origins.

"I looked through every near-Earth asteroid spectrum we had access to,
and nothing matched," said Sharkey, the paper's lead author.

The debate over Kamo`oalewa's origins between Sharkey and his adviser,
UArizona associate professor Vishnu Reddy, led to another three years
of hunting for a plausible explanation.



==========================================================================
"We doubted ourselves to death," said Reddy, a co-author who started the project in 2016. After missing the chance to observe it in April 2020
due to a COVID-19 shutdown of the telescope, the team found the final
piece of the puzzle in 2021.

"This spring, we got much needed follow-up observations and went,
'Wow it is real,'" Sharkey said. "It's easier to explain with the moon
than other ideas." Kamo`oalewa's orbit is another clue to its lunar
origins. Its orbit is similar to the Earth's, but with the slightest
tilt. Its orbit is also not typical of near-Earth asteroids, according
to study co-author Renu Malhotra, a UArizona planetary sciences professor
who led the orbit analysis portion of the study.

"It is very unlikely that a garden-variety near-Earth asteroid would spontaneously move into a quasi-satellite orbit like Kamo`oalewa's,"
she said.

"It will not remain in this particular orbit for very long, only about
300 years in the future, and we estimate that it arrived in this orbit
about 500 years ago," Malhotra said. Her lab is working on a paper to
further investigate the asteroid's origins.

Kamo`oalewa is about 4 million times fainter than the faintest star the
human eye can see in a dark sky.

"These challenging observations were enabled by the immense light
gathering power, of the twin 8.4-meter telescopes of the Large Binocular Telescope," said study co-author Al Conrad, a staff scientist with
the telescope.

The study also included data from the Lowell Discovery Telescope in
Flagstaff, Arizona. Other co-authors on the paper include Olga Kuhn,
Christian Veillet, Barry Rothberg and David Thompson from the Large
Binocular Telescope; Audrey Thirouin from Lowell Observatory and Juan
Sanchez from the Planetary Science Institute in Tucson. The research
was funded by NASA's Near-Earth Object Observations Program.

========================================================================== Story Source: Materials provided by University_of_Arizona. Original
written by Mikayla Mace Kelley. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Benjamin N. L. Sharkey, Vishnu Reddy, Renu Malhotra, Audrey
Thirouin,
Olga Kuhn, Albert Conrad, Barry Rothberg, Juan A. Sanchez,
David Thompson, Christian Veillet. Lunar-like silicate
material forms the Earth quasi-satellite (469219) 2016 HO3
Kamoʻoalewa. Communications Earth & Environment, 2021; 2 (1)
DOI: 10.1038/s43247-021-00303-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211111130321.htm

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