A NASA spacecraft, recently returned from a mission to the asteroid Bennu, was relaunched to study another asteroid as it neared Earth's orbit: Apophis, named after the Egyptian Chaos god. The space rock is expected to pass within 32,000 kilometers of Earth's surface on April 13, 2029.
On December 22, NASA announced that its OSIRIS-REx spacecraft had been relaunched to study a 370-meter-diameter asteroid approaching Earth orbit named Apophis.
In Egyptian mythology, Apophis is a serpent-shaped god and personification of darkness and disorder that seeks to destroy the world. Fortunately, the asteroid that bears its name doesn't think so.
Like Earth, Apophis orbits the Sun, and now and again, it almost makes contact with our planet. On April 13, 2029, the 40-50 million ton asteroid is expected to come within 32,000 kilometers of Earth, closer than some artificial satellites – something that has never happened in recorded history.
After five years, weather permitting, Apophis' path will be visible to the naked eye over Asia, the Indian Ocean, Australia, Africa and much of Europe and part of the Pacific Ocean.
Old spacecraft, new mission
After a seven-year journey to the asteroid Bennu, OSIRIS-REx returned to Earth in September. After 4 billion kilometers of travel, the spacecraft still had a quarter of its fuel left and was sent to intercept Apophis.
Several destinations were considered, including Venus, although the Apophis mission was the winner. For its new mission, the spacecraft was renamed OSIRIS-APEX (Origination, Spectral Interpretation, Resource Identification and Protection – Apophis Explorer).
The mission will cost $200 million, according to NASA.
Apophis is an “S-type” asteroid composed of silicate and nickel-iron materials, which differs from carbon-rich “C-type” asteroids like Bennu.
As the asteroid nears Earth, OSIRIS-APEX will pass within 25 meters of Apophis' surface to extract as much information as possible. Of particular interest to scientists is “how the surface changes as it interacts with Earth's gravity,” Amy Simon, the mission's principal investigator at NASA's Goddard Space Flight Center, said in a NASA press release.
Interacting with Earth's gravity can trigger earthquakes and landslides on the asteroid, which then shake the object. “A close encounter of Apophis with Earth will change the asteroid's orbit and the length of its 30.6-hour day,” NASA said.
“We know that tidal forces and accretion of debris piles are fundamental processes that can play a role in planet formation,” said Dani Mendoza della Giustina, principal investigator of the OSIRIS-APEX mission at the University of Arizona. “They can shed light on how we evolved from the debris of the early solar system to full-fledged planets.”
Although most known hazardous asteroids (orbits within 4.6 million kilometers of Earth) are S-type, Apophis' proximity to Earth allows research into planetary defense, one of NASA's top priorities.
Collision with Earth is ruled out
The discovery of Apophis at Arizona's Kidd Peak Observatory in 2004 raised concerns and still fuels theories about a possible collision with Earth. “Apophis is coming, that's why they're building bunkers.” Reading a user's post on X.
In the early stages of discovery, the asteroid was classified as a level 4 on the Torino scale (used to classify the risks of impacts from near-Earth objects, such as asteroids or comets, on a scale of 0 to 10). – Always classification.
But in December 2004, just months after the asteroid was discovered, updated modeling proved the possibility of an Earth impact to be almost zero.
Also, in June 2021, Apophis passed 17 million kilometers from Earth, allowing NASA to correct calculations and categorically rule out the possibility of a collision.
Rejecting the “don't look” scenario, NASA officially removed Apophis from it. Earth's closest approaches list.
After the asteroid passes, OSIRIS-APEX will operate near it for 18 months to study changes in Aophis near Earth.
This article has been translated from French.