Category Archives: Comets and Asteroids

So No New Earth Trojans, But OSIRIS-REx’s MapCam Surpassed Expectations

Asteroid 12 Victoria, imaged by NASA’s OSIRIS-REx spacecraft on Feb. 11. Credits: NASA/Goddard/University of Arizona.

Remember when I mentioned that NASA’s OSIRIS-REx spacecraft was going to be scanning for “Trojan” asteroids at Earth-Sun L4? Well the results are in and survey says: no new Trojans (besides 2010 TK7, which we already knew about.) But the search wasn’t in vain—it gave mission scientists a chance put the spacecraft’s OCAMS instruments to the test and they passed with flying colors.

In fact the MapCam camera did so well it was able to image 17 main belt asteroids from L4, some two full magnitudes dimmer than expected.

“The Earth-Trojan Asteroid Search was a significant success for the OSIRIS-REx mission,” said OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, Tucson. “In this first practical exercise of the mission’s science operations, the mission team learned so much about this spacecraft’s capabilities and flight operations that we are now ahead of the game for when we get to Bennu.”

Read the full story on the OSIRIS-REx site here: OSIRIS-REx Asteroid Search Tests Instruments, Science Team


Rolling Boulders on a Comet

A 100-foot-wide boulder on the surface of Comet 67P/C-G (ESA/Rosetta/MPS)

See that big rock there? (It’s easy because there’s a big yellow arrow pointing to it.) That’s a 100-foot/30-meter wide boulder that was imaged sitting on the surface of Comet 67P/Churyumov-Gerasimenko by ESA’s Rosetta on May 2, 2015. Nine months later Rosetta captured another image of the same area in which that huge stone had clearly moved—find out below just how far!

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NEAR Showed Us a Rocky World of Love

The asteroid Eros imaged by NEAR Shoemaker on March 3, 2000. (NASA/JPL/JHUAPL)

The asteroid Eros imaged by NEAR Shoemaker on March 3, 2000. (NASA/JPL/JHUAPL)

This image of the asteroid Eros—named after the Greek god of love—was captured on March 3, 2000, by NASA’s NEAR Shoemaker spacecraft. It’s actually a mosaic of six separate images acquired from a distance of 127 miles from the 20-mile-wide asteroid, and reveals many large boulders scattered across the surface down to about 160 feet in size. The ubiquitous boulders on Eros are believed to be fragments of its own native rock, shattered by countless impact events over time.

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OSIRIS-REx Captures a Picture of Jupiter from L4

Jupiter imaged by OSIRIS-REx on Feb. 12, 2017. The visible moons are Callisto, Io, and Ganymede. (NASA/Goddard/University of Arizona)

NASA’s OSIRIS-REx may be designed to study asteroids close up but recently it’s captured a view of something farther away and much, much larger: the giant planet Jupiter and three of its largest moons at a distance of over 400 million miles!

The image was taken on Feb. 12, 2017, when the spacecraft was 76 million miles (122 million km) away from Earth—near the Earth-Sun L4 point—and 418 million miles (673 million km) from Jupiter. It’s a combination of two images taken with the PolyCam instrument, OSIRIS-REx’s longest range camera, which will capture images of the asteroid Bennu from a distance of over a million miles.

Read the full article here: NASA’s OSIRIS-REx Takes Closer Image of Jupiter

Chelyabinsk: a Blast From the Not-Too-Distant Past (or, How’s That Space Program Coming Along?)

Dashcam video of the Chelyabinsk meteor exploding on Feb. 15, 2013 (Source:

Dashcam video of the Chelyabinsk meteor exploding on Feb. 15, 2013 (Source:

Four years ago today an explosion shattered the morning sky over the Chelyabinsk region in southwestern Russia, the result of a 60-foot-wide fragment of an asteroid entering Earth’s atmosphere at over 40,000 mph and brilliantly blowing itself to smithereens at 97,000 feet up. Even at that altitude, the resulting flash of light and air blast was powerful enough to cause extensive damage on the ground, shattering windows, knocking in doors, and causing injury to nearly 1,500 people across towns in the area—several of them seriously.

This was the largest observed meteor since the famous 1908 Tunguska event, but thanks to the prevalence today of dashboard and CCTV cameras in Russia this one was well-recorded. (I remember seeing the videos online within an hour after it happened!) The footage has allowed scientists to not only determine the energy of the Chelyabinsk meteor explosion—about 500 kilotons—but also the object’s trajectory and origin.

Watch a video below of footage captured from various locations of the Chelyabinsk meteor:

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Could This Asteroid Hit Earth? Astronomers Go “Back in Time” to Find the Answer

Potentially hazardous asteroid 2016 WJ1 was discovered in Oct. 2016—but also in July 2003. Credit: Canada-France-Hawaii Telescope

Astronomers are always watching the skies for observations of near-Earth asteroids—”space rocks” that have orbits close to Earth’s and, in the case of potentially hazardous asteroids (aka PHAs), those whose orbits could actually cross Earth’s and are larger than 150 meters (500 ft) across. When a new one of these is discovered—no small feat considering that many are very dark, move quickly, and could really be anywhere in the sky—it’s a scramble to determine the object’s orbital parameters and figure out just how close it can get to us and when. Such was the case on Oct. 19, 2016, when the asteroid 2016 WJ1 was identified with the Catalina Sky Survey. This object, estimated to be anywhere from 110 to 340 meters across—easily within the potentially hazardous range—was initially calculated to pose a threat in 2065 with a possible impact risk, albeit a very small one. Eventually though, scientists were able to refine the risk chance with more observations of 2016 WJ1…observations that had actually occurred over 13 years earlier.

Read the full story from ESA here: Asteroid sleuths go back to the future

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