Asteroids, Comets and NEOs Author: Sarah Roberts
Asteroids, Comets and NEOs - Introduction Impact craters form when an asteroid, comet or meteorite (which we collectively call impactors ) hits a planet or moon. The inner bodies of the Solar System have many impact craters on their surface, suggesting that they have been bombarded with impactors in the past. The images of Mercury and our Moon below illustrate just how common these impacts are. Mercury The Moon The Earth has also been heavily hit by impactors but due to erosion and weathering, as well as tectonic activity, the impact craters are continually disappearing. In this activity, the effect of impacts on planets and moons in the Solar System is investigated through the use of an online collision calculator. This can be found at: http://janus.astro.umd.edu/astro/impact/ Impact craters on the Earth Although the chances of asteroids or meteorites hitting the Earth are very slim, our planet has been struck in the past. There are a number of impact craters which are visible on our planet. These craters vary in size from small ( a few hundred metres) to very large (over 100km). The impacts causing this craters would, in turn, result in a variety of climatic changes - small impacts would generally affect only the local area, whereas larger impacts could have massive changes in the global weather systems. However, other factors also need to be considered when looking at the effect of impacts on Earth, such as the velocity that the impactor is travelling at, what the impactor is made from, and what it is landing on (e.g. land or sea). Page 2 of 6
Asteroids, Comets and NEOs - 1. Using the data given below for real impact craters on the Earth, investigate the effect of such impacts on our planet: Chicxulub, Mexico Target Composition of Diameter of Velocity of Earth (land only) rock 17.5km 20km/s Earth (water) rock 17.5km 20km/s Meteor Crater, USA Target Composition of Diameter of Velocity of Earth (land only) iron 50m 20km/s Earth (water) iron 50m 20km/s Target Earth (land only) Composition of Ries Crater, Germany Diameter of Velocity of rock 1500m 20km/s Earth (water) rock 1500m 20km/s Page 3 of 6
Asteroids, Comets and NEOs - 2. The amount of Kinetic Energy released during an impact is given by: K.E = 1 2 mv2 where m = mass of the impactor in kg v = velocity of the impactor in m/s K.E. = kinetic energy released in the impact, measured in Joules. The mass of an impactor can be calculated by: Mass = Density V olume and the volume of an impactor can be calculated by the following equation (if we assume a spherical impactor): V olume = 4 3 πr3 a) The Chicxulub Crater was formed by a rock impactor (density =2700 kg/m 3 ) with a diameter of 17.5km. Calculate the volume of the impactor, assuming it was spherical. Page 4 of 6
Asteroids, Comets and NEOs - b) Calculate the mass of the impactor which created the Chicxulub Crater. c) Finally, calculate how much Kinetic Energy was released in the impact, given that it was travelling at 20km/s. 3. Repeat question 2 (a)-(c) for the Meteor (iron impactor, density 8000kg/m 3 )and Ries Crater Impacts also. Which impact released the most amount of kinetic energy? Page 5 of 6
Asteroids, Comets and NEOs - Impact craters in the Solar System 1. Investigate the effect that an impactor similar to the one which caused the meteor crater in USA (iron impactor with diameter 50m and velocity of 20km/s), would have on the other planets in the Solar System. Solar System Body Mercury Venus the Moon Mars Jupiter Saturn Uranus Neptune Pluto Page 6 of 6