Asteroid 2012 DA14: Historic Earth Flyby of February 15, 2013

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Asteroid 2012 DA14: Near-Earth Asteroid

Detection and physical characteristics

This time, we saw it coming toward us as early as February 2012, and astronomers were able to detect it before its passage. Asteroid 2012 DA14 has a modest size of 45 meters and a mass of 135,000 tons. It approached Earth on February 15, 2013 at 7:24 PM (UTC).

Approach distance and comparison

Since the beginning of the near-Earth asteroid detection program, this asteroid is the largest object to have passed so close to Earth. The distance is still large enough to pose no collision danger, astronomers indicated. It will pass closest to Earth at 27,700 km, which represents a very small distance on the scale of the solar system; the Moon is at 360,000 km.

Origin and location in the solar system

Many small rocky bodies called asteroids are present in the solar system. A significant portion of them orbit in a ring between the orbits of Mars and Jupiter, between 2 and 4 AU, in what astronomers call the asteroid belt, also known as the main belt. It thus marks the boundary between the terrestrial planets and the gas giants.

Definition and impact frequency

An asteroid is a celestial object not visible to the naked eye due to its small size, ranging from a few tens of meters to several hundred kilometers in diameter. Objects less than 50 m in diameter, like asteroid 2012 DA14, are called meteoroids. "On average, an asteroid of this size approaches as close to Earth every forty years and is likely to collide with our planet every twelve hundred years," said Donald Yeomans, director of the Near Earth Object (NEO) office at NASA's Jet Propulsion Laboratory.

Potentially Hazardous Objects (PHOs)

PHO classification criteria

An asteroid is classified as a near-Earth object if its size is greater than 152 meters and its distance is less than 7.5 million kilometers from Earth. It is important to note that although these objects are described as "potentially hazardous," this does not mean that a collision with Earth is imminent or certain. Astronomers actively monitor these objects to calculate their future trajectories and assess the actual risks they pose. NASA has already cataloged 9,500 potentially hazardous small celestial bodies, or one-tenth of the total.

Impact scenarios and associated damage

An asteroid 45 meters in diameter that enters the atmosphere at a very shallow angle (a few degrees) fails to penetrate the atmosphere and causes no damage. It simply bounces off Earth's atmospheric layer and heads back into space. This occurred on August 10, 1972 in the skies over Montana in the northern United States. However, if it falls vertically, its size is sufficient to cause damage on the scale of a department (region). A 50-meter object creates a gigantic crater like the famous Meteor Crater in Arizona. By comparison, a 1 km meteorite would create a crater 20 kilometers in diameter and kill 2 to 3 billion people due to the tsunami triggered on the scale of a terrestrial hemisphere. The probability of this happening is once every 150,000 years.

The meteorite responsible for the extinction of the dinosaurs, which fell in the Gulf of Mexico 66 million years ago, measured 10 kilometers in diameter.

Largest known near-Earth asteroids

N.B.:
Near-Earth asteroids are classified into three main orbital families:
— Apollo asteroids have a semi-major axis greater than 1 AU and a perihelion less than 1.017 AU. They cross Earth's orbit and represent the majority of potentially hazardous objects.
— Amor asteroids have a perihelion between 1.017 and 1.3 AU. They do not cross Earth's orbit but can approach it under the effect of gravitational perturbations.
— Aten asteroids have a semi-major axis less than 1 AU and an aphelion greater than 0.983 AU. Their trajectory lies mainly inside Earth's orbit.
The table above presents the largest known specimens for each family, with their risk on the Torino scale (0 = no risk) and the estimated date of their next flyby.