Only 17 years after its discovery have we learned we’re safe from asteroid Apophis.
Ever since its 2004 discovery, asteroid 99942 Apophis has threatened planet Earth.
At 1100 feet (340 meters) across, an impact would release the energy equivalent of 1.2 Gigatons of TNT.
That’s ~100 times as energetic the Meteor Crater-creating impact.
Initially, observations indicated a 2% chance of a 2029 collision with Earth.
That alarmingly high probability arose from insufficient data.
In orbital mechanics, small positional uncertainties compound over time.
Gravitational encounters — including with major planets — further alter trajectories.
So do outgassing and interactions with unresolved objects.
Many high-resolution observations over long timescales can enable accurate predictions.
Now, in 2021, Apophis’s future trajectory is known through 2029: within ±2 km.
All potential impacts this century are confidently ruled out.
Still, many potentially hazardous objects, plus unidentified threats, remain.
Comet Swift-Tuttle, the Perseids’ parent body, remains Earth’s most dangerous object.
A possible 4479 collision could be 28 times worse than the historic Chicxulub impactor.
Observational identification with well-characterized trajectories are required to enact mitigation plans.
The Vera Rubin Observatory could help, but must overcome satellite megaconstellation pollution.
Otherwise, our fate will be to endure unforeseen damages, and then rebuild.
Detection and prevention offers the only catastrophe-free solution.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
Starts With A Bang is written by Ethan Siegel, Ph.D., author of Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.