Last year, NASA undertook its first planetary defense mission with the Double Asteroid Redirection Test (DART). The goal was to divert the moonlet Dimorphos from its orbit, demonstrating that an asteroid could be redirected in the case of a catastrophic course toward Earth.
The spacecraft’s impact, while altering the moonlet’s orbit, also resulted in the dispersal of 37 boulders from its surface. Some of these space rocks are as wide as 22 feet off its surface.
The DART mission was watched intently across the globe on September 26, 2022. The spacecraft successfully shifted Dimorphos’s orbit from an original 11 hours and 55 minutes to 11 hours and 23 minutes post-impact.
Unexpected DART results
While effectively showcasing the capability of humanity to potentially avert an asteroid disaster, this dramatic event also inadvertently created a ripple effect in space. The aftermath of the mission has brought forth a revelation that’s both intriguing and concerning.
The University of California, Los Angeles (UCLA) recently conducted a study analyzing the consequences of DART’s high-speed collision with Dimorphos.
David Jewitt, the leading astronomer behind the study, drew a vivid comparison to the aftermath. He likened the swarm of space rocks to a “cloud of shrapnel expanding from a hand grenade,” with velocities reaching up to 13,000 miles per hour.
“Because those big boulders basically share the speed of the targeted asteroid, they’re capable of doing their own damage,” explained Jewitt.
To put the potential dangers of these boulders into perspective, Jewitt mentioned that a 15-foot boulder, when colliding with Earth at such velocities, would unleash energy comparable to the atomic bomb that devastated Hiroshima during World War II.
DART boulders not a direct threat
However, it’s worth noting that none of the boulders resulting from the DART mission are on a trajectory to strike Earth.
Dimorphos itself was never a direct threat. Situated six million miles from our planet, it served as an ideal testing ground. The asteroid was proximate enough for observations yet distant enough to eliminate immediate repercussions.
How the research was conducted
The fascinating discoveries about the aftermath of the DART mission were made possible through images captured by NASA’s Hubble Space Telescope in December 2022.
These photographs revealed the boulders that had been dislodged from Dimorphos’s surface. This was either a result of the direct impact, or possibly from seismic vibrations caused by the collision.
DART’s pre-impact images showed boulders of similar sizes and shapes on the asteroid’s surface, further corroborating the findings from the Hubble telescope.
“The boulders we studied, among the faintest objects ever seen within the solar system, are observable in detail thanks to the powerful Hubble telescope,” said Jewitt.
“If we follow the boulders in future Hubble observations, we may have enough data to pin down the boulders’ precise trajectories. And then we’ll see in which directions they were launched from the surface and figure out exactly how they were ejected.”
The study, which has been published in the Astrophysical Journal Letters, highlights the complexities of space missions. While the DART mission is a testament to human ingenuity in the realm of planetary defense, it also serves as a reminder of the unpredictable nature of space and the cascading effects of our interventions.
More about planetary defense
Planetary defense refers to the strategies and methods developed to protect Earth from potential asteroid impacts. Given that our planet has a history of catastrophic impacts from space objects, the study and implementation of planetary defense mechanisms have become increasingly relevant. Let’s delve deeper into the subject:
Reason for concern
Throughout its history, Earth has been hit by space objects, such as the one believed to have caused the extinction of the dinosaurs approximately 65 million years ago. Although large impacts are rare, even a small asteroid impact in a populated area could result in significant casualties and destruction.
Detection and tracking
The first line of planetary defense is detecting Near-Earth Objects (NEOs) early. Various programs and telescopes worldwide, like the Pan-STARRS or the NEOWISE mission, continually scan the sky to identify and track these objects.
Once an NEO is identified, scientists work to determine its size, composition, structure, and potential impact trajectory. This helps in assessing the threat level and deciding on a suitable mitigation strategy.
Deflection and disruption
There are two primary approaches to prevent an asteroid from hitting Earth:
Deflection (DART mission example)
Changing the asteroid’s course so that it doesn’t collide with Earth. This could be achieved by a gravitational tractor (a spacecraft that flies alongside the asteroid for an extended period, using its gravity to subtly alter the asteroid’s path), kinetic impactors (like NASA’s DART mission), or other methods.
Breaking the asteroid into smaller pieces. One of the proposed techniques involves using a nuclear explosive device. However, this method is controversial due to the unpredictability of the asteroid fragments’ trajectories and the potential for radioactive contamination.
If an impact is imminent and cannot be prevented, evacuation and disaster management plans would need to be in place. Depending on the predicted impact site, governments might need to coordinate large-scale evacuations or prepare for post-impact relief and reconstruction.
Asteroid impacts are global threats, requiring international collaboration. The United Nations has recognized the importance of this through the Committee on the Peaceful Uses of Outer Space (COPUOS), which encourages member states to share data and strategies on NEO threats.
Engaging the public is essential. Education campaigns can achieve this, along with observing events like International Asteroid Day and involving amateur astronomers in tracking efforts.
Technological advancements will play a crucial role in planetary defense. Future missions, improved tracking systems, and new deflection techniques are all areas of active research and development.
More about asteroids
Asteroids, the rocky remnants from the solar system’s formation, continue to capture our attention and curiosity. These celestial wanderers often raise both wonder and concern. Here’s a comprehensive look at these enigmatic bodies.
What are asteroids?
Asteroids are rocky, airless fragments that orbit the Sun. Most of them lie in the Asteroid Belt, a region between Mars and Jupiter. They range from tiny pebbles to about 940 kilometers in diameter.
Origins and composition
Scientists believe asteroids are building blocks left over from the early solar system’s formation about 4.6 billion years ago. These bodies primarily consist of rock, metal, and sometimes organic compounds.
Classification of asteroids
Based on their composition, we classify asteroids into three main types:
- C-type (Carbonaceous): These constitute the majority of asteroids and contain carbon or carbon-rich materials.
- S-type (Silicaceous): Primarily composed of silicate materials and nickel-iron.
- M-type (Metallic): Mostly made up of metallic nickel and iron.
The Asteroid Belt
The majority of known asteroids reside in the Asteroid Belt. This vast region contains millions of asteroids, but it’s mostly empty space. Their collective mass amounts to less than that of Earth’s moon.
Near-Earth Asteroids (NEAs)
These asteroids have orbits that come close to Earth’s. Of these, some have orbits that intersect Earth’s, leading to potential impacts. Astronomers closely monitor these bodies to predict any possible collisions.
- Ceres: The largest asteroid and the only dwarf planet in the Asteroid Belt. It holds a significant amount of ice water.
- Vesta: The brightest asteroid visible from Earth. NASA’s Dawn spacecraft visited it in 2011.
- Pallas and Hygiea: Large asteroids with unique compositions that intrigue researchers.
Asteroids and Earth
Throughout Earth’s history, asteroids have impacted our planet. The most notorious event occurred 65 million years ago, contributing to the extinction of the dinosaurs. While large impacts are rare, they can have catastrophic consequences.
With advancements in technology, the idea of asteroid mining has gained traction. Companies and governments view asteroids as potential sources for rare metals and water. This exploration could revolutionize industries and support deep-space missions.
Humanity has sent various missions to explore asteroids. These missions provide insight into the early solar system and Earth’s formation. For instance, NASA’s OSIRIS-REx mission recently collected samples from the asteroid Bennu, aiming to return them to Earth for analysis.
To safeguard our planet, scientists and engineers develop strategies to divert or destroy hazardous asteroids. These techniques range from gravitational tugging to direct collision methods.
Asteroids, far from being mere rocks in space, offer a glimpse into our solar system’s history. As we continue to study and interact with them, they might unlock secrets of the past and pave the way for future space endeavors.