Earth-like planet lost atmosphere due to giant collision in nearby star system


With renewed interest in asteroids and objects coming from deep space and the risks of a potential collision with Earth, astronomers have arrived for the first time on a planet that could have lost its atmosphere due to ‘a collision with a giant object.

A team of astronomers have detected an Earth-like planet that may have lost part of its atmosphere due to a collision 200,000 years ago. Astronomers from MIT, the National University of Ireland Galway and the University of Cambridge have discovered evidence of the giant impact in a nearby star system, just 95 light years from Earth. Dubbed HD 172555, the star is around 23 million years old and scientists suspect its dust bears traces of a recent collision.

The study published in the journal Nature indicates that It is through these giant impacts that planets like young Earth reach their final mass and achieve long-term stable orbital configurations. A key prediction is that these impacts produce debris. Astronomers have reported “the detection of a carbon monoxide ring co-orbiting with dusty debris around HD172555 between about six and nine astronomical units – a region analogous to the region of the outer terrestrial planet of our solar system.”


Star HD 172555 had been a source of intrigue among astronomers due to an unusual composition of its dust, which likely contains large amounts of unusual minerals, in much finer grains than astronomers would expect. Tajana Schneiderman, a graduate student in the Department of Earth, Atmospheric, and Planetary Sciences at MIT, who led the study, examined data from the Atacama Large Millimeter Array (ALMA) in Chile in search of signs of carbon monoxide around nearby stars.

The ALMA Observatory is a network of 66 radio telescopes whose spacing can be adjusted to increase or decrease the resolution of their images.

“When people want to study the gas in debris discs, carbon monoxide is usually the brightest, and therefore the easiest to find. So we looked at the carbon monoxide data for HD 172555 again, because it was an interesting system, ”said Schneiderman. The team was able to detect carbon monoxide after further analysis of the data and found that the gas made up 20% of the carbon monoxide found in Venus’ atmosphere.


The gas was spinning in large quantities, surprisingly close to the star, at about 10 astronomical units, or 10 times the distance between the Earth and the sun. The presence of gas in such large quantities around the star called for an explanation and the researchers worked on different scenarios.

Astronomers worked on a scenario in which the gas came from the debris of a newly formed star, as well as a scenario in which the gas was produced by a close belt of icy asteroids, but they were excluded. The best-fitting scenario the team considers is that the gas was a holdover from a giant impact.

“Of all the scenarios, this is the only one that can explain all the characteristics of the data. In systems of this age, we expect there to be giant impacts, and we expect giant impacts to be really quite common. The time scales are arranged, the age is arranged, and the morphological and compositional constraints are arranged. The only plausible process that could produce carbon monoxide in this system in this context is a giant impact, ”Schneiderman said in a statement.

The team estimates that the gas was released by a giant impact that happened at least 200,000 years ago, recent enough that the star did not have time to completely destroy the gas. Based on the abundance of the gas, the impact was likely massive, involving two proto-planets, likely comparable in size to Earth.

Astronomers speculate that the impact was so large that it likely blew out part of a planet’s atmosphere, in the form of the gas the team observed today.

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