In recent years, movies like “Armageddon” and “Deep Impact” about have shown asteroids threatening the Earth and showing devastating effects from impacts. Planetary defense efforts and the possibility of such events are not just science fiction.
NASA and the European Space Agency (ESA) have been working together to learn about potential dangers from asteroids and other near-Earth objects. They have also taken concrete steps to be able to protect us if a dangerous asteroid did come our way.
DART Planetary Defense Mission Deflects Asteroid
On 24 November 2021, NASA launched the Double Asteroid Redirection Test (DART) on a Falcon 9 rocket from Vandenberg Air Force Base. The goal of this planetary defense initiative was to strike an asteroid with a spacecraft moving at high speed to try to change its orbit and deflect it away from Earth.
DART also carried a small satellite from the Italian Space Agency (ASI). This was the Light Italian CubeSat for Imaging of Asteroids (LICIACube). It was about the size of a shoebox. It split apart from DART several days before the impact.
The target for the DART mission was the Dimorphos moonlet, which orbits the larger asteroid Didymos. Dimorphos is about 6.8 million miles from Earth Neither object was a threat to Earth, but they were relatively close considering the vast distances between objects in space. Didymos is about a half mile in diameter, and Dimorphos is about 525 feet in diameter.
DART reached the Didymos system on 26 September 2022 and recorded its own images up to a few seconds before the impact. These images were able to pinpoint the exact impact site within one meter. DART struck Dimorphos 7:14 p.m. and it took 38 seconds for signals confirming the successful impact to reach Earth. DART was moving at about 14,000 miles per hour at impact.
Detailed Images from Satellites and Telescopes Provide Proof of Successful DART Mission
The LICIACube was able to take detailed images of Dimorphos from before and just three minutes after the impact. These showed debris around Dimorphos following the collision, important confirmation of the success of this planetary defense initiative.
The mission then shifted to analyzing the effect of the collision. Since DART’s impact with Dimorphos, astronomers have been using ground-based telescopes, the LICIACube, and the Hubble Space telescope to observe it. Their investigation has confirmed that DART did change Dimorphos’s orbit around Didymos.
“This result is one important step toward understanding the full effect of DART’s impact with its target asteroid” said Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters in Washington.
European Space Agency Launches HERA Mission to Study DART Impact
To perform a follow-up observation of DART, the ESA launched its Hera mission on 7 October 2024 to revisit Didymos and Dimorphos. Hera, which ESA calls “Europe’s Flagship Planetary Defender,” launched on a Falcon 9 Rocket from Cape Canaveral.
Hera should reach the Didymos system in January or February of 2027. Scientists hope it will provide important information useful for future planetary defense efforts.
A Boost from Mars on Hera Mission
The trip will require several complex maneuvers including passing within about 3100 miles of Mars. This will use the planet’s gravity to accelerate the spacecraft.
“We are very fortunate that Mars is in the right place at the right time to lend a hand to Hera,” says Pablo Muñoz from ESOC’s Mission Analysis team, who planned Hera’s journey. “This enabled us to design a trajectory that uses the gravity of Mars to accelerate Hera towards Didymos, offering substantial fuel savings to the mission and allowing Hera to arrive at the asteroids months earlier than would otherwise be possible.”
Hera to Examine Impact of DART Mission
Once Hera arrives at the Didymos system, it will begin series of close observations. It will perform five observation passes, each getting closer to the surface of Didymos. On its fourth pass, Hera will fly at about 3100 feet above the surface and eventually land on Dimorphos.
During the mission, Hera will examine the density and shapes of Didymos and Dimorphos. It will also observe changes in the movement and orbit of Dimorphos and closely examine the impact crater from DART.
European Center Maintains Data on near-Earth Objects
All of this work to study ways to protect Earth from asteroids and other objects is based on real data. In recent years, the ESA has been keeping track of objects from its Near-Earth Object Coordination Centre (NEOCC), the operational center of its Planetary Defense Office. It gathers information from telescopes and other sensors.
The NEOC is at ESA’s ESRIN site in Frascati, Italy. It is the the central access point for an entire network of European near-Earth object data sources. The NEOC uses the data to study orbits, monitor impacts, and analyze potential risks. This includes giving nations timely data regarding objects moving close to Earth.
A near-Earth object is an asteroid or comet which passes close to the Earth’s orbit. This means it is within about 28 million miles of Earth’s orbit. The NEOCC also has a website with current information and statistics on asteroid numbers, upcoming close asteroid flybys, and ESA’s asteroid risk list.
As of November 2024, there are more than 1,200,000 asteroids in our Solar System. Over 36,000 are near-Earth objects, and more than 1700 are on ESA’s risk list, meaning that they deserve close follow-up observations. This provides critical information for all international planetary defense efforts.
Video showing HERA Planetary Defense Mission to Didymos Asteroid System. Image: ESA
