Topic: Space

NASA's DART mission revealed that asteroids with smaller companions can exchange rocks and dust through gentle impacts. This discovery was made by analyzing images taken just before the spacecraft intentionally collided with an asteroid moon.

Astronomers have long known that some asteroids come in pairs, orbiting each other in a binary system. But they thought these systems were pretty quiet, with the two bodies simply moving around each other. However, a new study shows that these paired asteroids are actually quite active, exchanging rocks and dust through slow-moving impacts.

The discovery was made by analyzing images taken by NASA's Double Asteroid Redirection Test (DART) spacecraft in 2022. The spacecraft intentionally collided with the asteroid moon Dimorphos, which is part of a binary system with its larger companion Didymos.

In those images, scientists noticed bright, fan-shaped streaks on Dimorphos' surface. These markings provided the first direct visual proof that material can naturally travel from one asteroid to another.

The study's lead author, Jessica Sunshine, explained that these streaks are like 'cosmic snowballs' being thrown between the two asteroids. The results were published in The Planetary Science Journal and could help scientists better understand asteroids that might one day threaten Earth.

The researchers also found evidence of a process called the Yarkovsky-O'Keefe-Radzievskii-Paddak (YORP) effect, which causes small asteroids to spin faster as they absorb sunlight. This increased spin can lead to loose material being flung off the surface and sometimes forming a small moon.

The study's findings were made possible by months of careful analysis by researchers Tony Farnham and Juan Rizos. They developed specialized techniques to remove shadows and lighting artifacts from the photos, allowing them to reveal the subtle streaks left by the 'cosmic snowballs'.

Why It Matters

This discovery can help scientists better understand asteroids that might one day threaten Earth. It also highlights the importance of studying binary asteroid systems, which are surprisingly common in our region of the solar system.

Key Facts

• 15% of asteroids that pass near Earth have a smaller companion orbiting them
• Binary asteroid systems can exchange rocks and dust through slow-moving impacts
• The YORP effect causes small asteroids to spin faster as they absorb sunlight

Key Terms

Yarkovsky-O'Keefe-Radzievskii-Paddak (YORP) effect

A process that causes small asteroids to spin faster as they absorb sunlight

Implications

This discovery can help scientists better understand asteroids that might one day threaten Earth. It also highlights the importance of studying binary asteroid systems, which are surprisingly common in our region of the solar system.