Scientists Explain the Physics Behind 2 Asteroids Hitting the Same Location Simultaneously

One asteroid hitting a planet could cause devastating damage, such as what happened 66 million years ago when it caused the extinction of dinosaurs. But how about two asteroids striking at the same time in the exact location?

A new study investigates this phenomenon on Mars which likely received impacts from binary asteroids given its hundreds of craters. But study lead author Dmitrii Vavilov from the Côte d'Azur University in France noted that it is difficult to find double craters that resulted from a double asteroid impact.

Physics Behind Double Asteroid Impact

In 1993, NASA's Galileo spacecraft was traveling to Jupiter, observing an asteroid called Ida on the way, when mission scientists spotted a second asteroid orbiting nearby. They were so confused and debated if they saw it wrong. However, they were not mistaken with what they saw - Ida became the first confirmation of binary asteroids.

The study titled "Evidence for Widely-Separated Binary Asteroids Recorded by Craters on Mars," published in the journal Icarus, investigates binary asteroids hitting Mars.

Based on observations, scientists estimate that one in every six asteroids is part of a binary system. According to Wired, some examples are in the solar system, particularly in the asteroid belt between Mars and Jupiter. Didymos and its small companion, Dimorphos are the best example of binary asteroids and are now the target of NASA and ESA to test their asteroid defense system.

It is not easy to find craters made by a double asteroid impact, but since craters on Mars remain visible for billions of years scientists decided to study them. They used high-resolution images of the surface taken by Mars orbiters and examined almost 32,000 craters larger than 4 kilometers.

As a result, they found 150 pairs that appeared to be the result of a double asteroid impact. Their shapes include teardrop craters, peanut craters, and double craters, depending on the position of the two asteroids at the time of impact.

They make up just 0.5% of the total craters on Mars and most of them have similar sizes, which contradicts the leading theory of how binary asteroids are made. So, they investigated the age of some of these craters to study their evolution throughout the solar system. Scientists said their work helps scientists know what happens to binary systems when they grow older.

They also noted that they could go beyond Mars for more evidence of binary craters, such as on Mercury or the dwarf planet Ceres which is in the middle of the asteroid belt.

Double Asteroid Impact on Earth

In 2014, a team of researchers outlined some evidence for a double asteroid impact on Earth using tiny, plankton-like fossils that showed neighboring craters in Sweden were the same age. They presented their findings at the 45th Lunar and Planetary Science Conference in Texas.

Although there were possible double impacts that were already known on Earth, Dr. Jens Ormo told BBC News that there are disputes over the exact timeline of these craters. He cautioned that these craters must be of the same age to be considered a result of a double asteroid impact; otherwise, they are just two craters next to each other.

Binary asteroids are believed to have formed when a rubble pile asteroid spin so fast due to sunlight that it gets thrown out from its equator and transforms into a small moon. Space observations reveal that around 15% of near-Earth asteroids are binaries, although they are less likely to hit Earth. Estimates suggest that only around 3% of impact craters on Earth are caused by binary asteroids.

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