Planetary Defense - Protecting Earth from Asteroids
Asteroids are ancient space rocks from the Solar System’s formation. Until March 2019, there were more than 600 thousand known asteroids on our Solar System, and of these, 20 thousand were near-Earth objects (NEO) and 800 in the ESA risk list. NEO is any natural object orbiting around the sun and within a distance smaller than 50 million km from Earth.
Even with all the technical evolution made over the years, it is still impossible to know all the asteroids. Especially the ones closer to the sun, the light conditions make it very difficult and sometimes impossible to see them, even with the special telescopes in the USA, Chile, Spain, and Italy. However, there is a discussion among astronomers to build a space telescope to see those rocks and even place it on the moon’s surface. The moon would shield the telescope from radiation and lights coming from Earth and provide a better view.
What are the consequences of an impact?
Although we can observe and determine where those spatial bodies are, we don’t have a response if an asteroid is heading to Earth. We have the technology available to mitigate the situation, but it was never tested in realistic conditions.
An impact from large rocks, such as the one that wiped out non-flying dinosaurs from Earth, is rare. However, small asteroids with only 150m-diameter are very common and can release three times the earthquake’s energy that happened in Tohoku, Japan, 2011, inflicting devastating regional damage. Even if the asteroids disintegrate on Earth’s atmosphere and never reach the ground, it can create explosive airburst resulting in shockwaves. As in 2013, in Chelyabinsk, Russia, which resulted in over a thousand people injured during a small asteroid explosion.
It is estimated that one km or more asteroids could devastate a whole continent, and the dust from the impact could cause drastic cooling and negatively impact crops worldwide for a few years. The consequences asteroids strike on Earth depend on several factors, such as the location of the impact, the trajectory, and the asteroid’s physical properties. Currently, there is no understanding of those properties, which is critical to mitigation response tolls and techniques.
Credits: Tomi Kärkkäinen/ Reaktor Space Lab
What are the mitigation response techniques available?
There are several options for asteroid defense, sending astronauts to explode one, like in the movie Armageddon is just not one of them. All the proposals involve robotic spacecraft instead. The risk of having Earth hit by a piece of debris resulting from the explosion is too high. The best method depends on the response time available and the size of the asteroid.
Most of the techniques involve changing the trajectory of the object in direction to Earth. The kinetic impactor is the most mature technique, due to the usage of existing and affordable spacecraft technology. The kinetic impactor changes the asteroid’s orbit by colliding with it at a certain speed. However, the larger the body, the more difficult it is, demanding a more significant impact.
Also, to determine the viability of this technique, a better understanding of the debris formation resulting from the collision is necessary, and how much kinetic energy from the impactor may go into fragmentation and restructuring or kinetic energy of the ejected material. It is critical to understand better the impactor momentum transfer connection with properties of the NEO target and the relative velocity vector of the impactor in the impactor momentum transfer. As well if, all the parameters apply to many asteroids or only for taxonomic type.
If a massive rock is to hit Earth, there is a hazardous possibility of detonating a nuclear bomb near the asteroid, to vaporize part of its surface and change its course. However, Earth could still be hit by a fragment. As in many cases, such as climate change and the pandemic, preparations make the difference.
In this case, the Japanese Space Agency (JAXA) is a step further with the launch of the asteroid sample-return mission Hayabusa2 in 2014. The spacecraft traveled 300 million km to reach the asteroid Ryugu in June 2018. The mission is using the German-French probe to collect info about the asteroid surface, decisive info to plan and execute an asteroid deflection maneuver and will re-enter Earth in December 2020.
ESA and NASA have a Planetary Defense Office to handle subjects related to Earth protection from danger coming from space, including asteroids.
Credits: ESA
What is ESA doing to protect Earth?
ESA’s office regularly conducts observations campaigns to look for dangerous space rocks, predicts their orbits, produces impact warnings when necessary, and is involved in potential mitigation measures, dividing the work into three areas, observation, data provision, and mitigation. It intends to become aware of NEOs positions relative to Earth, estimates the impact’s probability and consequences, informs relevant parties if necessary, and develop methods to deflect risks asteroids. Besides supporting European observations, ESA conducts its own, using a 1-m-diameter telescope at the Optical Ground Station in Tenerife.
This telescope is not the only one used by ESA to provide orbit determination, impact monitoring, data provision, and risk analysis. ESA’s NEO Coordination Center (NEOCC) uses Minor Planet Center information, which is operated with help and support of the International Astronomical Union (IAU), in the USA, and uses Telescopes and radar systems worldwide. NEOCC is the access point for the European asteroid data sources and information provider network.
ESA also has plans to use a Flyeye telescope to scan the skies for space rocks. The bug-eyed telescope would scan the entire sky in 48 hours. And a 56cm Test-Bed Telescope (TBTs) will test the data processed by the Flyeye telescope. ESA is also developing a space-based fireball camera and tolls to simulate impacts and their effects on Earth and investigate deflection techniques. ESA’s Space Safety & Security activities goal is to mitigate and prevent the consequences of hazards from space.
Credits: NASA
What is NASA doing to protect Earth?
On the other side of the pond, as determined by the White House, a National NEO Preparedness Strategy and Action plan will be followed by NASA and Federal Emergency Management Agency (FEMA). The aim is to prevent dangerous asteroids from colliding with Earth and preparing the US if that happens.
The action plan has five main goals:
To reduce uncertainty and help a more accurate decision, NASA will lead new efforts to enhance USA’s capabilities for detecting, tracking, and characterizing NEO. At this moment, NASA supports ground-based asteroids observatories. However, it will need to identify opportunities in existing and planned telescope programs to enhance the volume and quality of data streams.
The second goal is to improve modeling, prediction, and information integration across American agencies, which will enhance the previsions of collisions probability and when and where it would hit Earth.
NASA also was asked to provide new ways to deflect asteroids and develop new technologies for rapid-response NEO surveillance missions.
Increasing international cooperation to better prepare the world in case of an asteroid strike is part of the plan. For that, NASA’s Planetary Defense Coordination Office is working together with the United Nations Committee on the Peaceful Uses of Outer Space. The committee has an international network of asteroids tracking astronomers and observatories (International Asteroid Warning Network), sharing useful data about NEO.
The final main goal requests an action plan to go in effect if a massive asteroid were to hit Earth with little to no warming. It requires improvement and training of NEO impact emergency procedures and action protocols.
A double mission called AIDA (Asteroid Impact Deflection Assessment) was conceived in international cooperation to understand more about asteroids and experience deflective techniques. NASA will launch the Double Asteroid Redirection Test (DART), followed by ESA’s mission Hera. Our next pots will talk about those two missions.
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This article was written by Juliane Verissímo - Marketing Department of VisionSpace