OSIRIS-REx visits the most dangerous asteroid in the world

On April 25, NASA announced its decision to extend eight interplanetary missions. Some of them got new goals. The most interesting task got the spacecraft OSIRIS-REx. It will have to visit the 370-meter asteroid Apophis (99942 Apophis), once considered the most dangerous asteroid in the Solar System.

Asteroid Apophis

Apophis was opened in 2004. Preliminary calculations carried out after the discovery of the asteroid caused a sensation. They showed that there is an about 2.7% probability that Apophis will collide with Earth on April 13, 2029.

Near Earth asteroid in the artist’s image. Source: NASA/JPL-Caltech

According to experts, when Apophis collided with the Earth, energy equivalent to an explosion of 1200 megatons of TNT would be released. An impact on land would lead to the formation of a five-kilometer crater and the devastation of thousands of square kilometers of territory. The fall of Apophis into the ocean would lead to the emergence of a giant tsunami that covered the coasts of many countries.

Model of the surface of the asteroid Apophis. Source: UArizona/JPL/Arecibo

It is not surprising that for a while Apophis became the number one topic in the world news. Fortunately, it quickly became clear that the preliminary estimates of its danger were overestimated. More detailed calculations showed that in 2029 the asteroid will make a close approach to Earth at a distance of 38 thousand km. However, there was a small chance that this approach would change the orbit of Apophis in such a way that it would collide with our planet in 2036. But subsequent observations exclude any possibility of an asteroid falling to Earth within the next hundred years.

OSIRIS-REx is heading to Apophis

Although Apophis has lost the title of the most dangerous asteroid in the world, it is still of great scientific interest. And its approach to Earth in 2029 will be one of the main astronomical events of the decade. Apophis will pass inside the orbits of geostationary satellites and will be visible in the Earth’s sky with the naked eye. It is not surprising that many space agencies have long considered the possibility of sending an automatic scout to the asteroid. 

OSIRIS-REx near the surface of the asteroid Apophis. Source: Heather Roper

And recently, NASA has found an option on how to study Apophis. The choice of the aerospace administration fell on the OSIRIS-REx spacecraft, which is currently returning to our planet with samples of the matter of the asteroid Bennu. In September 2023, it will drop a capsule with the collected materials to Earth, after which it will be “released”. At the same time, all the systems of the device are working normally, and it has a significant fuel reserve left, allowing it to visit some other small body. After analyzing all the available options, NASA management decided to send the spacecraft to Apophis. The mission will change its name to OSIRIS-APEX (OSIRIS-APophis EXplorer).

OSIRIS-APEX will reach Apophis in April 2029, just a few days after its approach to Earth. Over the next 18 months, the spacecraft will study the asteroid and how Earth’s gravity affected its orbit. In addition, OSIRIS-APEX will perform several maneuvers, during which it will approach Apophis, and then activate its engines. This operation should expose the subsurface layers of the asteroid and allow us to study their structure and chemical composition.

You can also read about China’s plans to change the orbit of a potentially dangerous near Earth asteroid.

According to https://www.asteroidmission.org