NASA‘s OSIRIS-REx probe, which brought precious samples of the Bennu asteroid to Earth, is now engaged in a long journey to study another asteroid, Apophis. The spacecraft has embarked on a secondary mission to explore and approach Apophis, an asteroid that was once considered a threat to Earth.

The spacecraft took advantage of its return near Earth to set course for Apophis. It fired its engines about 20 minutes after releasing the re-entry capsule containing uncontaminated material from Bennu.

Near Venus in 2029

Complex journey will take the probe much closer to the Sun than originally planned. Passing by Venus several times, OSIRIS-REx will encounter the asteroid Apophis, also known as asteroid 99942, on April 8, 2029. This time, the probe will not collect samples from Apophis but will study the asteroid for 18 months.

These proximity operations will include imaging and mapping of the asteroid and a close rendezvous maneuver like the one used to obtain material from Bennu in October 2020. Although we won’t be able to analyze parts of Apophis on Earth, this maneuver will provide unique information about its subsurface, composition, and properties.

Apophis is an intriguing and high-profile near-Earth object. It was once thought that the approximately 340-meter object had the potential to collide with Earth in 2068. Today, it is no longer considered a threat, and the celestial dance of the Solar System will instead offer the opportunity to get closer to this object.

Apophis vs. Bennu

The next close approach of Apophis to Earth will pass at about 32,000 kilometers from us on Friday, April 13, 2029. While some may consider it an ominous date, it offers humanity a great opportunity to study the asteroid and learn more about the evolution of the solar system. “Apophis is a typical near-Earth asteroid” said Olivier Hainaut, an astronomer working on Near-Earth Objects (NEO) at the European Southern Observatory (ESO).

“By studying it, we will learn more about these objects, most of which formed in the same place as Earth” Hainaut said. “In a way, you can consider Apophis and NEOs as crumbs left over from the creation of Earth”. Bennu is a carbon-rich Type B asteroid, but Apophis is a Type S asteroid, composed mainly of silicate and nickel-iron.

These relics from that primordial era are common in the inner solar system and could reveal untold secrets about the origin of planets and the processes that led to their formation. Due to their common properties, they will also be useful for planetary protection efforts. “It’s very interesting from a scientific point of view and very interesting for Earth protection” Hainaut said. “Even though Apophis is not dangerous, we expect it to be very similar to other NEOs that could potentially collide with Earth”.

Multiple Close Encounters

But an asteroid may not be what it seems. OSIRIS-REx discovered that Bennu had a surface that behaved surprisingly like a ball pit. So, we won’t know what Apophis is like until the probe sees it up close. NASA’s Small Bodies Assessment Group recently asked the agency to find a way to fly close to Apophis before its close encounter with Earth.

The group stated that it would “provide a comprehensive investigation of this extraordinary opportunity. Quantify and understand in real-time the consequences of planetary tides and asteroid evolution. Gather crucial information about Apophis’s internal structure, which would otherwise be unobtainable” the group said.

Elsewhere, a workshop is being organized for 2024 (ref.) to explore opportunities for international collaboration for both Earth-based observations and potential in-situ investigations of Apophis. Whether these extra missions occur or not, OSIRIS-REx will provide additional pieces of the puzzle.

Sofia Bianchi
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