Skip to main content
  1. Home
  2. Space
  3. News

A tiny pebble could have caused the dramatic self-destruction of a 5-mile-long asteroid

Georgina Torbet
By
The asteroid 6478 Gault is seen with the NASA/ESA Hubble Space Telescope, showing two narrow, comet-like tails of debris that tell us that the asteroid is slowly undergoing self-destruction. The bright streaks surrounding the asteroid are background stars. The Gault asteroid is located 214 million miles from the Sun, between the orbits of Mars and Jupiter. NASA, ESA, NASA, ESA, K. Meech and J. Kleyna (University of Hawaii), O. Hainaut (European Southern Observatory), L. Calçada

Hubble has observed something unusual in the sky — a self-destructing asteroid called 6478 Gault, or simply Gault for short. But what caused it?

The Gault asteroid, named after planetary geologist Donald Gault, is between four and nine kilometers long (that’s 2.5 to 5.6 miles) and has a distinctive double tail. The two comet-like tails of debris are evidence of activity in which the asteroid is ejecting material into space, suggesting that Gault is breaking apart.

Recommended Videos

The asteroid is disintegrating due to a process called YORP torque (short for the Yarkovsky–O’Keefe–Radzievskii–Paddack effect) which is caused by the scattering of solar radiation. Sunlight hits the asteroid and heats it, producing infrared radiation which is sent out into space and which carries heat and momentum with it. This creates a force which in rare cases can make an asteroid spin faster.

As the asteroid spins faster and faster, the centrifugal force pulling the asteroid apart eventually becomes more powerful than the gravitational force holding it together. When this happens, rocks and dust are pulled off the surface of the asteroid and create a tail of debris.

“This self-destruction event is rare,” Olivier Hainaut of the European Southern Observatory, Germany, explained in a statement. Of the 800,000 asteroids in the belt between Mars and Jupiter, astronomers estimate that only one YORP disruption is seen per year.

But Hubble and other new telescopes are now able to view these wild asteroids as they disintegrate. “Active and unstable asteroids such as Gault are only now being detected by means of new survey telescopes that scan the entire sky,” Hainaut said, “which means asteroids such as Gault that are misbehaving cannot escape detection any more.”

Gault is important not only because it is rare to see a YORP event in action but also because it is believed to have a rotation period of two hours, which is right on the border of the speed required for the YORP effect to kick in. “Gault is the best ‘smoking-gun’ example of a fast rotator right at the two-hour limit,” lead author Jan Kleyna of the University of Hawaiʻi, confirmed in the statement. “It could have been on the brink of instability for 10 million years. Even a tiny disturbance, like a small impact from a pebble, might have triggered the recent outbursts.”

One tiny pebble, eh?

The findings will be published in The Astrophysical Journal Letters.

Topics
Georgina Torbet
Georgina Torbet
Space Writer
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Starliner spacecraft just took a major step toward first crewed flight
Boeing's Starliner spacecraft being stacked on the Atlas V rocket.

A crane lifts the Starliner spacecraft to the top of an Atlas V rocket. Boeing Space

Boeing’s CST-100 Starliner spacecraft has been stacked atop the United Launch Alliance (ULA) Atlas V rocket ahead of its first crewed flight next month.

Read more
NASA needs a new approach for its challenging Mars Sample Return mission
An illustration of NASA's Sample Return Lander shows it tossing a rocket in the air like a toy from the surface of Mars.

NASA has shared an update on its beleaguered Mars Sample Return mission, admitting that its previous plan was too ambitious and announcing that it will now be looking for new ideas to make the mission happen. The idea is to send a mission to collect samples from the surface of Mars and return them to Earth for study. It's been a long-term goal of planetary science researchers, but one that is proving costly and difficult to put into practice.

The Perseverance rover has already collected and sealed a number of samples of Mars rock as it journeys around the Jezero Crater, and has left these samples in a sample cache ready to be collected.  However, getting them back to Earth in the previous plan required sending a vehicle to Mars, getting it to land on the surface, sending out another rover to collect the samples and bring them back, launching a rocket from the planet's surface (something which has never been done before), and then having this rocket rendezvous with another spacecraft to carry them back to Earth. That level of complexity was just too much to be feasible within a reasonable budget, NASA Administrator Bill Nelson announced this week.

Read more
Final communications sent to the beloved Ingenuity Mars helicopter
NASA’s Ingenuity Mars helicopter is seen here in a close-up taken by Mastcam-Z, a pair of zoomable cameras aboard the Perseverance rover. This image was taken on April 5, the 45th Martian day, or sol, of the mission.

Earlier this year, the beloved Mars helicopter Ingenuity ended its mission after an incredible 72 flights. Originally designed as a technology test intended to perform just five flights, NASA's helicopter was the first rotorcraft to fly on another planet and was such a success that it has already inspired plans for more exploration of distant planets using rotorcraft. Its mission came to an end, however, when it damaged one of its rotors, leaving it unable to safely fly.

Even then, the helicopter was still able to communicate by sending signals to the nearby Perseverance rover, which acted as its base station. Now, though, Perseverance is traveling away from the helicopter to continue its exploration of Mars. So this week, the NASA team on the ground met for the last time to communicate with Ingenuity, bringing the mission to a final close.

Read more