UC Berkeley Berkeley Scientific Journal
Title Collision Course: The Threat and Effects of an Asteroid Impact
Permalink https://escholarship.org/uc/item/68q7q2f4
Journal Berkeley Scientific Journal, 17(2)
ISSN 1097-0967
Author Reddy, Sharath
Publication Date 2013
DOI 10.5070/BS3172020099
Undergraduate
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T C n the winter of 2012, believers in the Mayan sure waves that felled trees for 30 miles, an lub that formed about 65 million years ago, it actually occurring. Comparing the threat prophecy predicting the cataclysmic destruc- impact which was more powerful than the precisely when the K-Pg (Cretaceous Paleo- of an asteroid impact to the threat of other tion of the Earth on December 21st, 2012 atomic bomb dropped on Hiroshima (Phil- gene) extinction occurred. Asteroid impacts geological threats allows us to gain a better Iwere disappointed when life continued on lips, 2008). Villagers living nearly 40 miles are point events, which lead to a longer term understanding of the relative threat an NEO the 22nd. Although that may have been a from the blast epicenter were eyewitnesses effects such as a decrease in temperature and poses. Megatsunamis caused by massive un- “near miss” for the planet’s inhabitants, a to the event, communicating what they saw death of vegetation, which would eventually dersea earthquakes and volcanic supererup- new threat is just upon the horizon: asteroids, to Russian geologists and astronomers. This cause the extinction of dinosaurs (Alvarez, tions such as the Yellowstone Caldera com- comets, and meteoroids, all poised for a path effects of this impact resulted from an asteroid 1983). In more recent years, with the advent prise some such possible geological threats. dangerously close to our home. only a few tens of meters across. What NASA of radiometric dating, the formation of the Both supereruptions and megatsunamis occur With the recent Russian meteor impact on and other space agencies are searching for are Chicxulub crater has been placed to be within much more frequently, about once every February 15th, 2013 (Wall, 2013), and a host asteroids which are a kilometer long, much of other nearby impact candidates, an aster- larger than a few tens of meters. The destruc- oid impact is an important global threat that tive capabilities of such an asteroid are dif- must be investigated. These asteroids, com- ficult to imagine, but there is at least one such ets, and meteoroids which pose a significant impact which scientists have studied. threat to the Earth are collectively known as The archetypal example of an asteroid caus- near-Earth objects (NEOs), defined as comets ing the extinction of entire species is the and asteroids that have been nudged by the Cretaceous mass extinction, which occurred gravitational attraction of nearby planets into about 65 million years ago. Although fossils BSJ orbits that allow them to enter the Earth’s of dinosaurs had already been found in rock neighborhood (LSST 2003). Among these was strata across the globe, the reason as to why asteroid 99942 Apophis, which in 2004 was they were there was not as well understood. BSJ predicted to collide with the Earth in the year Luis Alvarez, a physicist from UC Berkeley, 2029. NASA has since determined that there is and his son Walter (currently a professor at no longer any significant probability of im- UC Berkeley), began studying rock strata pact; however, considering the sheer number using radioisotopes present in the differ- of NEOs in our solar system, investigating the ent layers. While studying the layer of strata possible threats and effects of such an impact formed between the Cretaceous and Paleo- is a necessity. gene geological periods, they found levels of the element Iridium to be much higher than hen an asteroid collides with another in regular rock strata. massive object (e.g. the earth), the orrelating this fact with the knowledge kinetic energy of the asteroid is con- that asteroids were known to contain high Wverted into heat and sound, creating pressure concentrations of Iridium, Alvarez posited waves which travel radially outwards from Cthat an asteroid must have made impact be- the impact center, similar to that of an atomic tween those periods depositing sediment con- bomb. However, an asteroid has the potential taining high levels of Iridium on rock strata. to be much more devastating than an atomic Since fossils of dinosaurs were found only in bomb: an asteroid just a few tens of meters Cretaceous strata (66 million years ago) and across can yield the energy equivalent of ten older, this led to the formulation of the Alva- to fifteen megatons of TNT (Institute of Phys- rez hypothesis, which theorizes that the cause Figue #2 The frequency of asteroid mpacts on Earth ics). An asteroid of this size was the perpetra- of the extinction of dinosaurs was an asteroid tor of the 1908 Tungsuka event, during which impact. One valuable piece of evidence in 33,000 years of the time of the K-Pg extinction. 50,000 years; the last major asteroid impact an asteroid exploded midair in a sparsely support of this hypothesis is a large crater General acceptance of the Alvarez Hypothesis event was 65 million years ago, although populated region of Siberia, releasing pres- on the Yucatan peninsula of Mexico, Chicxu- by the scientific community has also followed, smaller asteroids hit every couple decades cementing the notion of asteroids as the har- (such as the Tunguska event and the recent bingers of mass extinction. An NEO such as Russian meteor). In fact, the earth is constant- “When an asteroid collides with another massive object (e.g. the that which collided with the Earth 65 million ly bombarded by smaller particles originating years ago poses just as great a threat to hu- in the asteroid belt. Objects a meter across earth), the kinetic energy of the asteroid is converted into heat and manity as it did to the dinosaurs. impact on a yearly basis. However, more cata- sound, creating pressure waves which travel radially outwards strophic events are much rarer, occurring tens from the impact center, similar to that of an atomic bomb.” n order to visualize the threat an asteroid of millions of years apart. (Image #2) Aster- poses, we have to consider two things: mag- oid impacts would have a much larger range Initude of the event, and the probability of of devastation relative to a megatsunami or 2 • Berkeley Scientific Journal • Death and dying • Fall/Spring Year • Volume #17 • Issue #2 Berkeley Scientific Journal • death and dying • Fall/Spring Year • Volume #17 • Issue #2 • 3 volcanic supereruption; for instance, the temperatures landslide of the La Palma island in the At- (like during lantic Ocean could trigger a megatsunami the Cretaceous “For example, some astrobiologists which would devastate the eastern sea- mass extinc- board of the US, but few other places of tion) is about hold that meteors were actually the world would be affected. An asteroid 1 kilometer. the vector of life, bringing a kilometer across would almost certainly At the impact microorganisms formed have global effects (McGuire, 2006). site, multiple hile a 1 kilometer asteroid impact events will elsewhere in the universe to only happens once every 600,000 occur. First, a earth, a theory known as lthoughA as- years, the magnitude of the aster- massive cra- panspermia.” teroids and Woid impact is very great compared to the ter will form other NEOs other two possible geologic events. Even where the may have a though impact rates have been stable NEO collides, leading to a massive release reputa- tion as civilization threaten- for 50,000 years, the impact of an object of heat and sound in the form of a firestorm; ing, they also have life bringing capabilities. greater than 1.5 kilometers in diameter this will lead to the complete obliteration of For example, some astrobiologists hold that would have a global effect, causing an flora and fauna in the immediate impact area, meteors were actually the vector of life, bring- ing microorganisms formed elsewhere in the estimated 1.5 billion deaths (Bland, 2005). Figure #1 The discovery of known near-Earth asteroids. which can be up to ten times the size of the Compared to the other possible geological actual asteroid. Wildfires around the impact universe to earth, a theory known as pansper- BSJ threats the earth faces, an asteroid would site would lead to more loss of life and smoke mia. Furthermore, asteroids played a key role affect the largest area and cause the most ranging from ground based optical telescopes blocking the sun. Earthquakes could also oc- in the development of modern civilization deaths. Furthermore, the statistical probabil- to infrared space telescopes with the purpose cur up to Richter magnitude 13, potentially and the rise of humans. As Luis and Walter BSJ ity of dying due to an asteroid is 1 in 20,000; of observing and predicting the movements altering the orbit of the Earth. Alvarez discovered, the impact of a large this relatively high number is due to the very of potentially hazardous asteroids and comets here would also be long-term effects on the asteroid during the Cretaceous period led to high magnitude an impact would have. If (LSST, 2003). Some are capable of predict- climate: within hours of the impact, a glob- the extinction of dinosaurs, allowing the rise an asteroid were to collide, even if it hap- ing the orbital paths of an asteroid for the al firestorm would start due to the reentry of mammals as the dominant animal life form pens very rarely, you would have a higher next century; some probes are being sent to Tof ejecta back into the Earth’s atmosphere on the planet. This in turn would lead to the chance of being killed. One reason the threat already detected comets in order to collect (Nelson, 2011). Dust caused by the impact evolution of apes, and eventually humans of impact is diminished is because discovery samples (Evans et al., 2003). would block sunlight, leading to continual (Institute of Physics). Of course, this doesn’t of a potentially dangerous near Earth object problem which persists, even with ad- darkness, death of vegetation, food shortage, really help out the current human population. usually occurs a decade or more in advance, vanced asteroid detection technologies in and death. The ozone would also be affected However, steps are being taken to protect us giving us ample time to mount a defense place, is the recurring impact of smaller by a large impact, leading to increased ex- from NEOs: the United Nations is currently against such an impact. Considering all of Aasteroids, like the one that recently hit Russia. posure of UV radiation to Earth (Edwards, discussing possible international defense these factors, the overall threat of an aster- They are too small to be detected by cur- 2010). This is because an impact in the ocean systems and missions to predict and protect oid impact still comes out to be lower than a rent technologies put in place to find NEO’s, would eject water vapor containing chlorine humanity from such a threat (David, 2013). megatsunami or supereruption (Bland, 2006). meaning they could continue to collide with and bromine high into the atmosphere, lead- And although there are thousands of other the Earth with little to no warning (Wall, ing to reactions similar to those caused by asteroids circling around the solar system, lthough the probability of an NEO im- 2013). The NASA Near Earth Object Program CFCs, resulting in the creation of a massive pact is small compared to other geologic is charged with finding only objects which ozone hole. The depletion of ozone leads to catastrophes, the massive magnitude an are 1 kilometer or larger; the recent Russian another serious effect: global warming, pos- Aimpact would have calls for investigation and impact was only 15 kilometers wide, yet it sibly for centuries. This would affect not only detection of these Near Earth Objects. Most was still able to injure hundreds. Less than the climates of areas, but also the flora and NEOs come from the Kuiper belt, an icy area one percent of asteroids that are 40 meters or fauna that live there, possibly changing entire exterior to Pluto with abundant comets, and larger have been detected, meaning the vast ways of life. Another possible consequence from the Asteroid belt, between Mars and majority are still out there without our knowl- of an ocean impact is a large tsunami which Jupiter. NASA has been attempting to cata- edge (Wall, 2013). could flood the interior of continents, causing log the majority of the large NEO population devastating short term damage, but also long in a reasonable amount of time, setting their nowing the threat posed by NEOs allows term changes on the populations that near initial estimates for about a decade (Pilcher, astrophysicists to predict the effects of these areas (Paine, 2011). Clearly, the threat 1998). Following an increase in funding from an impact. These effects are categorized and effects of an asteroid impact are very real, only $1.5 million per year (1998) to $16 mil- Kby the Torino Impact Scale, which ranks and have potentially disastrous consequences. lion (2012), the rate of discovery of new NEOs impact candidates based on the kinetic en- ergy and the probability of the impact. The has increased exponentially (Image #1). Figure #3. The Torino Scale is for categorizing the Currently, there are multiple systems in place global threshold size of an asteroid hitting the earth and causing a catastrophic fall in global imact hazard associated with near-Earth Objects. 4 • Berkeley Scientific Journal • Death and dying • Fall/Spring Year • Volume #17 • Issue #2 Berkeley Scientific Journal • death and dying • Fall/Spring Year • Volume #17 • Issue #2 • 5 BSJ 6 •B http://lsst.org/lsst/science/scientist_solar_system LSST. objects. Retrieved from (2003).Nearearth resources/topic/archive/meteor/index.html impacts. Retrieved http://www.iop.org/ from Physics. (n.d.).Meteorandasteroid Institute of 14(2),199-220. Journal, LincolnLaboratory program. by the linear asteroids near-earth of and discovery Evans, J., Shelly, F., &Stokes, (2003).Detection G. deplete-ozone-layer.html http://phys.org/news/2010-10-asteroid-ocean- into oceancoulddepleteozone layer. Retrieved from Edwards, strike L.(2010,October2010).Asteroid reviewing-asteroid-impact-threat/ technology_and_science-space/t/united-nations- http://www.nbcnews.com/id/50840661/ns/ Retrieved impactthreat. asteroid reviewing from 17). United nations David, L.(2013,February Retrieved http://neo.jpl.nasa.gov/stats/ from statistics. A.(2012).Neodiscovery Chamberlin, and EngineeringSciences,363(1837),2793-2810. Philosophical Transactions: Mathematical,Physical Bland ,P. impactrateonearth. (2005).The Sciences,80,627-642. Academy of theNational of Proceedings 65 millionyears ago. many species impactledtotheextinctionof asteroid Alvarez, L.(1983).Experimentalevidencethatan References to facesuchathreat. global prioritywhichisexactlywhatweneed an asteroid impactmighthavemadethema to meetheadon.Thus,thecatastrophic effects straight forus,acollisionwhichwe’llbeable to react inthecasethatanasteroid isheaded tify NEOs,weare givingourselvesmore time with theadventofnewtechnologiestoiden- erkeley S cientific J ournal •D eath and dying •F all pictures/2009/4/7/1239100063941/Asteroid-002.jpg 6) http://static.guim.co.uk/sys-images/Books/Pix/ jpg/599px-The_Earth_seen_from_Apollo_17. thumb/9/97/The_Earth_seen_from_Apollo_17. 5) http://upload.wikimedia.org/wikipedia/commons/ Lutetia_closest_approach_(Rosetta).jpg 4) http://upload.wikimedia.org/wikipedia/en/1/1b/ png thumb/8/8a/Torino_scale.svg/400px-Torino_scale.svg. 3) http://upload.wikimedia.org/wikipedia/commons/ impactrecurrence.gif 2) http://www.tulane.edu/~sanelson/images/ 1) http://neo.jpl.nasa.gov/stats/images/web_total.png Sources Image news/russia-meteor-explosion-20130218 be thelast.Retrieved http://www.weather.com/ from Wall, 18).Russian meteorwon’t M.(2013,February cfm http://impact.arc.nasa.gov/gov_asteroidperils_3.from defense.Retrieved objectsandplanetary on nearearth hearings Pilcher, (1998,Mar21).UScongressional C. science-news/science-at-nasa/2008/30jun_tunguska/ years later. Retrieved http://science.nasa.gov/ from Phillips, T. (2008,June tunguskaimpact--100 30).The horsts/paine_indochina.pdf tektites?. Retrieved http://users.tpg.com.au/ from theAustralasian Paine, Sourceof M.(2011,February). tulane.edu/~sanelson/geol204/impacts.htm and massextinction.Retrieved http://www. from (2011,NovemberNelson, S. 16).Meteorites,impacts, 1909. Physical andEngineeringSciences,364(1845),1889- assessment. PhilosophicalTransactions: Mathematical, geophysical identificationand events: Threat W.McGuire, extreme (2006).Globalriskfrom /S pring Y ear •V olume #17• I ssue #2