Tiny asteroid discovered Saturday disintegrates over Africa

June 4, 2018 by Dc Agle, JPL/NASA
Artist's concept of a near-Earth object. Credit: NASA/JPL-Caltech

A boulder-sized asteroid designated 2018 LA was discovered Saturday morning, June 2, and was determined to be on a collision course with Earth, with impact just hours away. Because it was very faint, the asteroid was estimated to be only about 6 feet (2 meters) across, which is small enough that it was expected to safely disintegrate in Earth's atmosphere. Saturday's asteroid was first discovered by the NASA-funded Catalina Sky Survey, located near Tucson and operated by the University of Arizona.

Although there was not enough tracking data to make precise predictions ahead of time, a swath of possible locations was calculated stretching from Southern Africa, across the Indian Ocean, and onto New Guinea. Reports of a bright fireball above Botswana, Africa, early Saturday evening match up with the predicted trajectory for the asteroid. The asteroid entered Earth's atmosphere at the high speed of 10 miles per second (38,000 mph, or 17 kilometers per second) at about 16:44 UTC (9:44 a.m. PDT, 12:44 p.m. EDT, 6:44 p.m. local Botswana time) and disintegrated several miles above the surface, creating a bright fireball that lit up the evening sky. The event was witnessed by a number of observers and was caught on webcam video: www.youtube.com/watch?v=rnBvSNYy-EY

When it was first detected, the asteroid was nearly as far away as the Moon's orbit, although that was not initially known. The asteroid appeared as a streak in the series of time-exposure images taken by the Catalina telescope. As is the case for all asteroid-hunting projects, the data were quickly sent to the Minor Planet Center in Cambridge, Massachusetts, which calculated a preliminary trajectory indicating the possibility of an Earth impact. The data were in turn sent to the Center for Near-Earth Object Studies (CNEOS) at NASA's Jet Propulsion Laboratory in Pasadena, California, where the automated Scout system also found a high probability that the asteroid was on an impact trajectory. Automated alerts were sent out to the community of asteroid observers to obtain further observations, and to the Planetary Defense Coordination Office at NASA Headquarters in Washington. However, since the asteroid was determined to be so small and therefore harmless, no further impact alerts were issued by NASA.

Meteorite/ ZLAF9B2. Credit: Barend Swanepoel

"This was a much smaller object than we are tasked to detect and warn about," said Lindley Johnson, Planetary Defense Officer at NASA Headquarters. "However, this real-world event allows us to exercise our capabilities and gives some confidence our impact prediction models are adequate to respond to the potential impact of a larger object."

The ATLAS asteroid survey obtained two additional observations hours before impact, which were used by Scout to confirm the impact would occur, and narrowed down the predicted location to southern Africa. Infrasound data collected just after the impact clearly detected the event from one of the listening stations deployed as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. The signal is consistent with an atmospheric impact over Botswana.

"The discovery of asteroid 2018 LA is only the third time that an asteroid has been discovered to be on an impact trajectory," said Paul Chodas, manager of the Center for Near-Earth Object Studies (CNEOS) at JPL. "It is also only the second time that the impact location was predicted well ahead of the event itself."

Credit: JPL/NASA

The first event of this kind was the impact of asteroid 2008 TC3, which lit up the predawn sky above Northern Sudan on October 7, 2008. That was a slightly larger asteroid (about 13 feet, or 4 meters in size), and it was discovered a full 19 hours before impact, allowing for a large number of follow-up observations and a very precise trajectory to be calculated. The second predicted impact event was for 2014 AA, which was discovered only a few hours before impact on Jan. 1, 2014, in the Atlantic Ocean, leaving too little time for follow-up observations. The Catalina Sky Survey has been responsible for discovering all three of these small asteroids on trajectories, and all on the watch of the same observer, Richard Kowalski.

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8 comments

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Gigel
2.3 / 5 (3) Jun 04, 2018
Pretty many close-by asteroid flights discovered lately. I wonder why. Some possibilities:

1. Teams looking for them got better at it;
2. Earth passes through an unusually high density of asteroid bodies; maybe the remains of a comet/larger asteroid that have been spread out over time;
3. Both of the above; or something else.

No. 2 would be good to check; it would be a dangerous setting for the near future.
antialias_physorg
5 / 5 (6) Jun 04, 2018
Some possibilities:

...just more get reported.
Gigel
4 / 5 (1) Jun 04, 2018
Some possibilities:

...just more get reported.

Yes. And there can be a few reasons for that.

If more foxes get reported, either more people look out for them, or there are more foxes in the area.
antialias_physorg
5 / 5 (6) Jun 04, 2018
Just checked with the NEO close approach list
https://cneos.jpl.nasa.gov/ca/
There is no uptick in near earth encounters. This year is exactly the same as last year
rrwillsj
1 / 5 (1) Jun 04, 2018
There is more observational capacity, improving communications and increasing public awareness of such events.

Everybody deludes themselves that they are the only one in the world getting rained on. That the passing car that splashed the puddle of muddy water all over them? Did it on purpose! Hell, maybe the driver was malicious but it is our instincts to blame, to anthromorphise what we directly perceive.
antialias_physorg
5 / 5 (1) Jun 05, 2018
There is more observational capacity, improving communications and increasing public awareness of such events.

Yeah...It's a bit like everyone gets bombarded with news about batteries in electric cars catching fire and therefor gets the notion that these technologies are unsafe. But when you look at the actual numbers then e.g. a fire in an ICE vehicle is about 5 times as likely per kilometer traveled.

New technologies get reported on. Old technologies having their usual kinds of failures isn't 'newsworthy'.
Gigel
1 / 5 (1) Jun 05, 2018
I don't think my hypothesis no. 2 can be disproved based on available data. It probably cannot be proven either. So we're either better at seeing asteroids or there are more of them near Earth lately.
antialias_physorg
5 / 5 (3) Jun 05, 2018
Just because a particular hypothesis cannot be disproven doesn't give it any probability to be true, either.

Example:
"god exists"

This cannot be disproven. Does this mean that the chance that a god exists is 1% or 50% or 99%?. None of the above. It's just a random statement.

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