Astronomers predict that in about 5-1/2 years, an asteroid approximately the same width as the Empire State Building is tall will come within 20,000 miles (32,200 km) of Earth. This will be the closest any celestial object of that size has come to our planet in modern history.
NASA’s spacecraft, launched in 2016, is expected to be in position to closely examine this rare close encounter. The mission, led by University of Arizona scientists, aims to provide insights into planetary formation and gather knowledge that could aid in the development of a defense system against potential asteroid collisions with Earth.
Initially, the asteroid Apophis appeared to pose a significant impact threat to Earth when it was discovered in 2004, with scientists predicting a potential collision in 2029. However, refined observations have since ruled out any impact risk for at least another century.
Nevertheless, Apophis will come extremely close to Earth during its next approach in 2029, passing within a distance less than one-tenth of the moon’s distance and well within the orbits of some geosynchronous Earth satellites.
The spacecraft currently on its way to rendezvous with Apophis is OSIRIS-REx, which gained attention three years ago for collecting a soil sample from a different asteroid and returning it to Earth in a capsule that made a parachute landing in Utah in September.
Instead of retiring the spacecraft, NASA has renamed it OSIRIS-APEX (APophis EXplorer) and adjusted its trajectory to target Apophis. The details of the Apophis expedition were published in the Planetary Science Journal.
Apophis is an oblong, peanut-shaped stony asteroid believed to consist mostly of silicate materials, along with iron and nickel. It measures about 1,110 feet (340 meters) across and is expected to pass within approximately 19,800 miles (31,860 km) of Earth’s surface on April 13, 2029. During this time, it will be visible to the naked eye for a few hours, appearing as a point of reflected sunlight in the night sky over Africa and Europe.
Encounters with asteroids of this size passing so close to Earth are estimated to occur approximately once every 7,500 years. The Apophis flyby is the first such encounter predicted in advance.
The gravitational pull of Earth is likely to cause measurable disturbances to Apophis’ surface and motion, altering its orbital path and rotational spin. Tidal forces could trigger landslides on the asteroid and dislodge rocks and dust particles, creating a comet-like tail.
The spacecraft is set to observe Apophis’ Earth flyby as it approaches and catches up with the asteroid. These observations and data will be combined with measurements from ground-based telescopes to detect and quantify any changes Apophis undergoes during its close pass by Earth.
OSIRIS-APEX is scheduled to remain near Apophis for 18 months, orbiting, maneuvering around it, and even hovering just above its surface. It will use rocket thrusters to kick up loose material and reveal what lies beneath.
Apophis, like other asteroids, is a relic of the early solar system. Studying its mineralogy and chemistry, which have remained largely unchanged for over 4.5 billion years, can provide insights into the origin and development of rocky planets like Earth.
A close examination of Apophis could also provide valuable information to planetary defense experts about the structure and properties of asteroids. Understanding the composition, density, and orbital behavior of such celestial “rubble piles” increases the chances of devising effective strategies to deflect asteroids and mitigate impact threats.
Last year, NASA deliberately crashed a spacecraft into a small asteroid as part of a planetary defense test, altering its natural motion. This marked the first time humans have intentionally changed the trajectory of a celestial body.
Although Apophis is substantially larger than the crashed asteroid, it is still small compared to the one that caused the extinction of dinosaurs 66 million years ago.
While an Apophis-sized asteroid is not large enough to pose an existential threat to life on Earth, a hypersonic impact could devastate a major city or region, potentially causing tsunamis if it strikes the ocean.
“It wouldn’t be globally catastrophic in the sense of mass extinctions,” said Michael Nolan, deputy principal investigator for the mission at the University of Arizona. However, an impact would still fall under the category of a significant event.
Nolan added, “This thing is coming in at many miles per second if it hits. And at that speed, it kind of doesn’t matter if it’s made of gravel or ice or rocks or whatever. It’s just a big, heavy thing moving fast.”
The article was reported by Steve Gorman in Los Angeles and edited by Will Dunham. The Thomson RushHourDaily Trust Principles apply.
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