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An 'invisible threat': Swarm of hidden 'city killer' asteroids around
Venus could one day collide with Earth, simulations show
News
By Harry Baker published yesterday
A new study suggests that unidentified "co-orbital asteroids" around
Venus may have the capacity to impact our planet in the future, with potentially devastating consequences. However, there is no immediate
threat.

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An artist's impression of asteroids approaching Earth
An unknown number of potential city-killer asteroids could be hiding
near Venus and could pose a threat to our planet in the future, new simulations suggest. (Image credit: Getty Images)
A hidden swarm of "city killer" space rocks, known as co-orbital
asteroids, is likely hiding around Venus and could pose an "invisible
threat" to Earth over the coming millennia if the asteroids are not
found, new simulations suggest. However, there is no immediate danger to
our planet, researchers told Live Science.

Co-orbital asteroids are space rocks that orbit the sun alongside a
planet or other large body without truly orbiting the larger object.
There are currently 20 known co-orbitals around Venus rCo ranging from
"Trojan asteroids," which are fixed either in front of or behind a
planet in its orbital plane, to a closely circling "quasimoon," known as Zoozve rCo all of which likely originated from the solar system's main asteroid belt between Mars and Jupiter. Dozens of similar co-orbitals
also tag along with Earth, and more are being discovered all the time.

All of the Venusian space rocks are likely wider than 460 feet (140
meters) rCo large enough to be considered "city killers," meaning they
could potentially wipe out a heavily populated area if they impacted our planet.

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Although the co-orbitals pose no threat to us from afar, a close
approach to Earth could cause them to be pulled away from their
gravitational anchor rCo and thus put them on a collision course with our planet. Venus is one of our closest neighbors and comes closer to Earth
than any other planet rCo within around 25 million miles (40 million km)
at its nearest point rCo making its trailing asteroids a credible threat
to our world.

Related: Undiscovered extra moons may orbit Earth. Could they help us
become an interplanetary species?

A timelapse photo of asteroids whizzing past Venus

At least 20 co-orbitals orbit the sun alongside Venus. This time-lapse
image of the planet was taken by the Parker Solar Probe in 2021. (Image credit: NASA/APL/NRL)
Researchers think there are more hidden space rocks lurking around
Venus. All but one of the planet's known co-orbitals have eccentricities greater than 0.38, meaning they have very elongated trajectories around
the planet. This suggests there is an observational bias, likely because objects with lower eccentricities are probably being obscured by the
sun's glare.

Co-orbitals can also move around relative to Venus, which can change
their chances of colliding with Earth in the future. Previous research
has shown that this likely happens to the space rocks once roughly every 12,000 years rCo known as a co-orbital cycle.

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In a new study, which was uploaded May 21 to the preprint server arXiv
and is currently undergoing peer review, researchers carried out a
series of computer simulations to gauge whether hidden asteroids with
lower eccentricities could threaten Earth. To do this, the researchers "cloned" known co-orbitals with eccentricities below 0.38 and simulated
how they might behave over a 36,000-year period (three co-orbital cycles).

The simulations revealed that some of the newly added co-orbitals could
pose a threat to Earth during this period. However, the study offers no indication of how likely a future collision really is, because it is
"hard to predict" how many co-orbitals there really are, study lead
author Valerio Carruba, an astronomer at S|uo Paulo State University in Brazil, told Live Science in an email. "How many exactly is an open
question."

A timelapse photo of Venus transiting the sun

The sun's glare could be hiding additional co-orbitals around Venus.
This time-lapse image shows Venus transiting our home star in 2012.
(Image credit: NASA/Goddard/SDO)
"Exciting" asteroids
Since the new study was first uploaded, several media outlets have
overhyped the risk of an imminent collision, with several tabloids
claiming Earth could be hit by Venusian asteroids "within weeks." But
there is nothing in the study to support those claims.

"None of the current co-orbital objects will impact Earth soon," Carruba clarified.

Carruba has been disappointed by some of the reporting surrounding the
new study, but is glad the topic is being covered. "There has been some sensationalism about this research, and our work has been cited with
some liberties," he said. "But we hope that this attention could raise interest in a very exciting class of asteroids, which should be more
carefully monitored."

Related: 'Planet killer' asteroids are hiding in the sun's glare. Can we
stop them in time?

The researchers also highlighted the recent discovery of the city killer asteroid 2024 YR4, which was initially predicted to have a 2.3% chance
of colliding with Earth in 2032, before the odds were later downgraded
to zero. This was an important reminder of the importance of detecting
and monitoring potentially hazardous asteroids, they wrote.

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New observational tools rCo such as the Vera C. Rubin Observatory in
Chile, which will capture its first light later this year rCo will improve scientists' ability to spot dangerous space rocks, including Venus' co-orbitals, in the coming decades. However, it may also be prudent to
send a telescope to Venus' orbit to specifically hunt for these objects,
the researchers wrote.

"I believe that we should not underestimate their potential danger, but
I would not lose sleep over this issue," Carruba said. "Soon, our understanding of this population will improve."

Harry Baker
Harry Baker
Senior Staff Writer
Harry is a U.K.-based senior staff writer at Live Science. He studied
marine biology at the University of Exeter before training to become a journalist. He covers a wide range of topics including space
exploration, planetary science, space weather, climate change, animal
behavior and paleontology. His recent work on the solar maximum won
"best space submission" at the 2024 Aerospace Media Awards and was
shortlisted in the "top scoop" category at the NCTJ Awards for
Excellence in 2023. He also writes Live Science's weekly Earth from
space series.


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