In 5 and 1/2 years from now, astronomers predict, a asteroid about as wide as the Empire State Building is tall, will streak through space within 20,000 miles (32,200 km) of the earththe closest any celestial object of that size will have come to our planet in modern history.
When that happens, a spacecraft is launched NASA in 2016 is expected to be able to provide a detailed study of this rare close encounter.
The mission, led by University of Arizona scientists, is expected to provide insights into planetary formation and knowledge that can inform efforts to build a defense system against possible doomsday asteroid collisions with Earth.
At the time of its discovery in 2004, the asteroid Apophis, named after a demon serpent that embodies evil and chaos in ancient Egyptian mythology, appeared to pose a serious threat to Earth, with scientists predicting a potential collision in 2029. Sophisticated observations have since reigned supreme. out of any risk of impact for at least another century.
Still, its next approach in 2029 will bring the asteroid into a cosmic cat’s whiskers on Earth – less than a tenth of moon‘s distance from us and well within the orbits of some geosynchronous Earth satellites.
The spacecraft now headed for a rendezvous with Apophis is OSIRIS-REx, which made headlines by picking up a soil sample from another asteroid three years ago and sending it back to Earth in a capsule that made a parachute landing in Utah in September.
The second act of the spacecraft
Instead of retiring the spacecraft, NASA renamed it OSIRIS-APEX — short for APophis EXplorer — and fired its thrusters to set it on course for its next target.
The Apophis expedition was described in a mission summary published in the Planetary Science Journal.
Apophis, elongated and somewhat peanut-shaped, is a rocky asteroid thought to be composed mainly of silicate materials along with iron and nickel. With a diameter of about 1,110 feet (340 meters), it should pass within about 19,800 miles (31,860 km) of Earth’s surface on April 13, 2029, and become visible to the naked eye for a few hours, said Michael Nolan, deputy superintendent. to the mission at the University of Arizona.
“It won’t be this glorious show,” Nolan said, but it will appear as a point of reflected sunlight in the night sky over Africa and Europe.
A large asteroid passing this close to Earth is estimated to occur about once every 7,500 years. Apophis’ flyby is the first such encounter predicted in advance.
The tidal pull of Earth’s gravity is likely to cause measurable perturbations to the asteroid’s surface and motion, changing its orbit and rotational spin. Tidal forces can trigger landslides on Apophis, dislodging rocks and dust particles to create a comet-like tail.
The spacecraft is set to observe asteroid Earth flyby as it approaches and eventually catches up with Apophis. These images and data would be combined with ground-based telescope measurements to detect and quantify how Apophis changed as it passed Earth.
OSIRIS-APEX is planned to remain near Apophis for 18 months – orbiting, maneuvering around it and even hovering just above its surface, using rocket thrusters to kick up loose material and reveal what lies beneath.
Planetary Science and Defense
Like other asteroids, Apophis is a relic from the early solar system. Its mineralogy and chemistry are largely unchanged for more than 4.5 billion years, providing clues to the origin and evolution of rocky planets like Earth.
A close study of Apophis could provide planetary defense experts with valuable information about the structure and other properties of asteroids. The more scientists know about the composition, density, and orbital behavior of such celestial “debris piles,” the greater the chances of devising effective asteroid-deflection strategies to mitigate impact threats.
NASA deliberately crashed a spacecraft into a small asteroid last year in a planetary defense test that pushed the rocky object off its normal path, marking the first time humanity altered the natural motion of a celestial body.
Apophis is significantly larger than the asteroid, but tiny compared to the one that hit Earth 66 million years ago and wiped out the dinosaurs.
While not large enough to pose an existential threat to life on Earth, an Apophis-sized asteroid hitting the planet at hypersonic speed could still destroy a major city or region, Nolan said, with ocean impacts triggering tsunamis.
“It wouldn’t be globally catastrophic in the sense of mass extinctions,” but an impact “would definitely fall under the category of bad,” Nolan said.
“This thing comes in at many miles a second if it hits. And at that speed, it doesn’t really matter if it’s made of gravel or ice or rock or whatever. It’s just a big, heavy thing, that moves fast.” Nolan added.
© Thomson Reuters 2023