Avoiding Asteroids

“We’ve once believed to exist in a safe environment among the surrounding universe, until we discovered how often the universe throws rocks at us...”

The Falling Rocks

        Approximately 4.57 billion years ago, the solar system was formed during a gravitational collapse of a small part of a molecular cloud. Most of the mass concentrated on the center forming the Sun while the leftovers formed its protoplanetary disk. By the means of accretion, dust particles in the disk were able to accumulate mass and attract smaller objects by gravitation influence, forming the planets we know today. But there were still leftovers, those who accreted a certain amount of matter to gain shape, mass and volume, but were never comparable to the major objects. Wandering within the inner solar system, they are now known to civilization as “Asteroids”, and are mostly composed of rock. In a macroscopic view, asteroids orbit the Sun as per the huge gravitational influence, along with the rest of the solar system. Microscopically, its orbit varies due other external effects and smaller gravitational sources, which includes our dear Earth. Nearby asteroids could be caught to free fall in Earth’s gravitational well, which might be quite troublesome for those living on it.  

*"Earth Impacting Asteroid" by Kevin M. Gill is licensed under CC BY 2.0

Can I Get Some Extra Energy?

Imagine yourself picking up a rock and dropping it to the ground, what would happen? Possibly some ignorable marks on both surfaces, but they still stay intact and the citizens of eorðe would live on for another day. It would be good news that you and your rock failed to destroy civilization. The bad news is, however, with the same mechanism, asteroids could. The mad scientist minded you might wonder: “So what is the difference between my roadside rock and space rocks?”. As per the conversation of composition, basically none. But as per the most important component to destroy a planet, your rock would be the greatest failure to this family. Conventionally, one might relate the “important component” to “size”, but its true identity would be “Energy”, or more specifically, “Kinetic Energy”(the energy an object possesses due to its motion). A famous quote might sound acquainted to one's ears: “Energy cannot be created nor destroyed.”, whereas the largely ignored following would be “It's only transferred or transformed to another form”. Both combined holds true as the “Conservation of Energy”, which would be the fundamental reason for asteroids to worry about. The equation for kinetic energy would be ½*m*v^2 (this calculation is severely simplified for the energy of an asteroid, but it still provides an insight), where m stands for mass and v stands for velocity. It would be worth noticing that proportional characteristics of the equation would enable high velocities to contribute high energies, regardless of non-zero mass dimensions. The velocity for your rock would be less than 5m/s as it impacts the ground, but for asteroids: “the most common type of impactor, slam into the Earth at an average velocity of 18 km/s.”^[1]. Assume both the asteroid and your rock posses a relatively low mass of 1kg, velocity characteristics would still provide the asteroid an amount of ½*1*18000^2=162000000 J of impact energy to transfer compared to your rock which would contain less than 12.5 J. However, this provides the roadside rock devastating characteristics while meeting certain energy criterias and introduces the fundamental  concerns regarding asteroids. For the Death Star minds of you, it would be worth remembering the requirement of “somewhere around 10^32 joules.”^[2] to erase earth. We’ve now acknowledged that the energy of an impactor would be the main devastation factor rather than its size. But still, it would sound quite counterintuitive for a mindset to appreciate such conclusion due to conventional impressions suggesting considerably large sizes in comparison to earth. However, history has shown that even the most devastating asteroids, aren’t the proudest in size among its family.

A Field Trip Back In Time

        The first asteroids were known to civilization back in the 17th century, but were not considered an official global threat until the 1990’s. This was due to the emerging evidence suggesting the Cretaceous-Paleogene extinction event, which erased three quarters of the species including the dinosaurs, was caused by an asteroid. The impact crater found underneath the Yucatan Peninsula in Mexico suggested that the asteroid had an estimated diameter around 15km, compared to the Earth’s 12742 km diameter and 40075 km circumference. Additional to the growing concerns, the Shoemaker-Levy 9 Comet impact event on Jupiter during 1994 was observed to obtain a diameter of 1.8km across, but was capable of releasing the amount of  2510400000000000 J of energy during impact. The 1908 Tunguska event, which flattened 2150 square kilometers of forest, possessed a diameter around 60 m. The recently well known atmosphere-burned-up “Chelyabinsk meteor” during 2013 had an estimated diameter of 20 m, but still caused thousands of injuries and structural damage. These historical events heavily  suggest that energy, rather than a massive size, is the dominant factor for having devastating characteristics. This argument could be further reinforced by NASA’s assessment regarding this issue: “If a rocky meteoroid larger than 25 meters but smaller than one kilometer ( a little more than 1/2 mile) were to hit Earth, it would likely cause local damage to the impact area. We believe anything larger than one to two kilometers (one kilometer is a little more than one-half mile) could have worldwide effects.”^[3]. With such understanding of the scale of destruction relatively small asteroids could bring, humanity seeked for methods to mitigate such threat. However, none of these methods proved to be easy.

 Additional information on Cretaceous-Paleogene extinction event: https://youtu.be/ExNL1HJvP1

* "Asteroid danger explained" by european space agency is licensed under CC BY-SA 2.0

 Damn You Space Rocks

To mitigate a threat, the first priority would be to identify it. Which is the first problem that comes when dealing with asteroids: “...such objects are difficult to find because they are intrinsically faint, and their rapid motion when near the Earth complicates their detection.”^[8]. For instance, the 2013 “Chelyabinsk meteor” was not detected until it entered the atmosphere, while the asteroid “2019 OK”, which was estimated to be 57-130 m across, was not detected until a day before its close flyby. The second role of thumb for mitigating asteroids would be the ability to derive its orbit. This was also proven difficult for various reasons, as one significant cause being the Yorkvosky effect, a thermal effect that propels the asteroid into different directions. For reference, during the orbital determination for asteroid (99946) Apophis, the Yarkovsky effect was a main contribution to orbital uncertainty: “As the Yarkovsky effect will not be directly detected, the main contribution will be on the orbital uncertainty information.”^[4]. Without the fundamental orbital characteristics of the asteroid, any advanced mitigation technology would be useless. But suppose we were to identify and obtain the orbital characteristics and launch our measures, this doesn’t mean that trouble is out the door. Asteroids are weakly bounded under gravity, any type of kinetic impactor tempting to change the orbit may cause an aftermath of the asteroids breaking into separate pieces, each piece still significant in size to cause reasonable damage. It would also be worth noting that since asteroids obtain massive energy in motion, one kinetic impactor would possibly not be enough for effectively deflecting the target. Each of these situations would require more launches than estimated. These difficulties, however, do not render humanity hopeless as solutions could eventually be derived, but with its progress being heavily dependent on one precious element: Time.

* "Asteroid detected" by european space agency is licensed under CC BY-SA 2.0

I Want “Time” For Christmas

The more time we have, the more considerations, calculations and preparations could be made, along with larger error tolerances that ensure the development and mitigation process both to be more achievable and effective. If time is relatively sufficient (half to a century), space tractors would be the best choice by constantly applying forces to change the asteroid’s orbit without causing any additional problems. But due to the difficulties in detection and prediction of asteroids, it could be expected that most reponses fall into short responses. The most common type of mitigation method in this time frame, given current technology development and resources, would be kinetic impactors, as stated in NASA’s 2007 report to Congress: “Non-nuclear kinetic impactors are the most mature approach and could be used in some deflection/mitigation scenarios, especially for NEOs that consist of a single small, solid body.”^[5]. But success rates of such method, as mentioned, is highly dependent on time, as time restricted short responses impose an increased amount of unsolvable uncertainties. It would be worth mentioning that any short response required to intercept within months to a year would be impossible, given the current development of civilization. It couldn’t be emphasized enough as time is the best measure when it comes to mitigating asteroids, but since the probability of time insufficient  risks exist, humans seeked for methods that are more time efficient. And the nominated come with greater issues.

* "Asteroid collision course" by european space agency is licensed under CC BY-SA 2.0

Did Someone Say “Nuclear”?

        As science progressed in subatomic zones, we found ourselves holding the keys to one of the highest energies that could be obtained by civilization: Nuclear Fission. It soon attracted military industrial complexes and was made into the most worrisome weapons in civilization. It was used as threats during peaks of political conflicts and still being stored with a significant amount to destroy civilization. But it turns out, this “Doomsday” device might be a savior if its targets are not the souls on Earth, but the rocks in space. Nuclear response was long on the table for mitigating asteroids, proposed for short responses and is somewhat abundant in resources while containing the energy needed to be more efficient than traditional kinetic impactors. As per NASA’s assessment : “Nuclear standoff explosions are assessed to be 10-100 times more effective than the non-nuclear alternatives analyzed in this study.”^[5]. With such an efficient method already on the table with the core resource in large storage, the traditional “inefficient” methods would seem to be purely a waste of invaluable time. But as efficient nuclear methods could be at destroying asteroids, its same efficiency in civilization destruction shouldn’t be forgotten. And this is one of the many problems that surfaces when it comes to such threat-related social political issues.  

Who’s Name Is “Threats”?

        Human civilization consists of complex foundations and structures tangled together forming the society we know today. The endless internal conflicts continuously mark scars within the only intelligent species we know within a span of 46.5 billion light-years. With the advancement of science and the introduction of doomsday devices, the fear of humanity eventually destroying civilization came into the minds, and this still implies when facing threats from the heavens. As mentioned previously, nuclear responses are the most efficient way of dealing with a devastating asteroid. While this statement is true, it's also dangerous. The already well-known efficiency of nuclear weapons erasing locations, access and life on Earth during the last century eventually poked fear and gave birth to existing international laws and restrictions. The “Outer Space Treaty” signed by existing nuclear powers, bans the deployment and usage of nuclear methods in space. However, the oppositionists might still lurk in the dark, waiting for a moment to strike: “It’s not hard to envisage nuclear powers using the vague threat of “asteroids” as a pretext for developing new warheads, or even for launching nukes into space. And if they do so in unapologetic violation of international law, they’ll also circumvent all the checks and balances that the law can provide. That threat is maybe more worrying than the threat of some hypothetical space rock.”^[6]. Conflictingly, when an looming global catastrophe regarding asteroids requires the most efficient emergency short response, it would be an unforgivable misuse of critical time to engage in debates on whether to prioritize existing legislative restrictions or the survival of humanity. This paradox emphasizes the need for a global collaboration which emphasizes credibility and transparency within the coordination. It should prevent the exploitation by self-interest complexes by holding multilateral characteristics along with humanity’s survival among all priorities. It should have the ability to authorize the correct usage of nuclear response based on solid scientific data, and be able to prevent any kind of abuse of its kind. Non-nuclear related social issues are largely contributed by civil panic, but the existence of the previous collaboration would be useful as it could efficiently collaborate with governments on providing guidance and information. It also has advantages in coordinating resources to be flexible when dealing with any previously discussed non-nuclear mitigation difficulties, even if it downs to the inevitable.  

 The Ticking Clock

        Asteroids are floating space rocks within the inner solar system. Though they provide precious information about the history of our very own solar neighborhood, dangerous as they could be for obtaining massive energies while some of them stumble into the way of earth. Being hard to detect, predict, and mitigate, such existence poses continuous threats to civilization. Potential threats are continuously being found as new astronomical equipments become operational. As per the B612 foundation, a planetary defence organization that consists scientists and engineers from the major related research fields: “It's a 100 per cent certain we'll be hit [by a devastating asteroid], but we're not 100 per cent sure when.” ^[7]. It would be wise to begin preparing now as we know our best measure is time, and the clock is already ticking. Given all the cautions, if still, ignorance led to similar events like the Cretaceous-Paleogene extinction event, it would be questionable to pinpoint an asteroid for the destruction of civilization rather than civilization itself.

Works Cited:

1. “Impact Cratering Mechanics.” Lunar And Planetary Institute, www.lpi.usra.edu/exploration/training/illustrations/craterMechanics/#:%7E:text=Asteroids%2C%20the%20most%20common%20type,velocity%20of%2018%20km%2Fs. Accessed 28 May 2021.
2. Sutter, Paul. “How to Destroy the Earth in Three Easy Steps.” Space.Com, 22 Jan. 2019, www.space.com/43014-how-to-destroy-the-earth.html.
3. “Asteroid Fast Facts.” NASA, www.nasa.gov/mission_pages/asteroids/overview/fastfacts.html. Accessed 29 May 2021.
4. Farnocchia, D., et al. “Yarkovsky-Driven Impact Risk Analysis for Asteroid (99942) Apophis.” Icarus, vol. 224, no. 1, 2013, pp. 192–200. Crossref, doi:10.1016/j.icarus.2013.02.020.
5. “NEO Survey and Deflection Analysis of Alternatives Report”, NASA,                              Near-Earth Object Survey and Deflection Analysis of Alternatives Report to Congress March 2007 https://web.archive.org/web/20160303220543/http://www.nasa.gov/pdf/171331main_NEO_report_march07.pdf
6. Green, James. “Nuclear Weapons Might Save the World from an Asteroid Strike – but We Need to Change the Law First.” The Conversation, 24 Apr. 2019, theconversation.com/nuclear-weapons-might-save-the-world-from-an-asteroid-strike-but-we-need-to-change-the-law-first-115865.
7. Harper, Paul. “Earth Will Be Hit by Asteroid with 100% CERTAINTY – Space Experts Warn.” Dailystar.Co.Uk, 21 June 2018, www.dailystar.co.uk/news/world-news/asteroids-earth-space-apocalypse-meteor-1713341
8. Zhai, Chengxing, et al. “DETECTION OF A FAINT FAST-MOVING NEAR-EARTH ASTEROID USING THE SYNTHETIC TRACKING TECHNIQUE.” The Astrophysical Journal, vol. 792, no. 1, 2014, p. 60. Crossref, doi:10.1088/0004-637x/792/1/60.