NASA Images Hazardous Asteroids That Sailed Close to Earth

Jul 05, 2024

Matt Growcoot

A grid of 25 grayscale images shows different views of a rotating asteroid, revealing its uneven and irregular surface. The asteroid appears to tumble and turn as it floats in space, with varying shadows and contours visible in each frame. — The 500-foot-wide asteroid 2024 MK that came within 184,000 miles of Earth on June 29.

Scientists fret about the possibility of an asteroid hitting Earth with catastrophic consequences, just ask the dinosaurs.

So when not one but two asteroids passed relatively close to home soil last month, it was an opportunity to take a closer look at these potential harbingers of the apocalypse.

NASA used a 230-foot-wide radar system in California to transmit radio waves at the asteroids and received the reflected signals to the same antenna. This mind-blowing technology was able to create an image of what the asteroids look like.

2024 MK

The 2024 MK asteroid passed Earth at a distance of 184,000 miles. That’s less than the distance between the Moon and Earth (about three-quarters).

At 500 feet (150 meters) wide, this medium-sized asteroid has the potential to cause significant damage if it hit Earth.

A grid of radar images of Asteroid 2024 MK taken on June 30, 2024, by Goldstone Radar. The grid displays variations in the asteroid's surface and shape captured between 05:55:18 and 09:59:18 UT. The images are shown at 3.75 m x 0.5 Hz resolution. — The images collected by NASA will help further the understanding of potentially hazardous asteroids.

As its name suggests, the asteroid was first observed this year by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) at Sutherland Observing Station in South Africa.

As it passed Earth, the gravitational pull reduced its three-year orbit around the Sun by about 24 days. Calculations of its future travel predict that 2024 MK will not collide with Earth.

A grainy gray-scale image of a comet or asteroid in space, with a rugged surface that features highlights and shadows, indicating its uneven terrain. The object is slightly elongated and appears to be rotating against a black background dotted with small white spots, representing distant stars or image noise.

To image 2024 MK (seen in a GIF above), NASA used two different antennas: One to transmit the radio waves and one to receive. This “bistatic” radar observation allowed them to create detailed images of the asteroid’s surface, revealing concavities, ridges, and boulders about 30 feet (10 meters) wide.

2011 UL21

2011 UL21 passed Earth at a far greater distance (4.1 million miles), but that is a good thing because UL21 is almost a mile wide (1.5 kilometers wide) classifying it as a large asteroid that has potentially global consequences if it strikes Earth.

NASA’s radio wave imaging determines that UL21 is roughly spherical and that it has a tiny moon orbiting it from a distance of about 1.9 miles (3 kilometers).

A series of radar images displays the movement of asteroid (415029) 2011 UL21 from June 27, 2024, with a resolution of 37.5 meters by 3.1 Hz and 15.1 minutes per frame. Bright, rounded spots depict the asteroid's positions against a grainy background. — UL21 was a lot further away, hence the less clear image. The white circle at the bottom of the image indicates the moonlet orbiting the mile-wide asteroid.

It is believed that the majority of large asteroids are in a binary system like UL21 and the presence of a moonlet may help scientists understand more about how the asteroid formed.

Both asteroids are classed as “potentially hazardous”; generally not thought to be a threat but if something went wrong — like if they collided with an object — they could potentially start hurtling toward Earth.

Image credits:NASA/ JPL-Caltech.

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