Threats to Earth – Revision Pack (P2)
Asteroids:
Asteroids are mini-planets or planetoids which orbit the Sun:
- They mostly orbit between the 4th planet (Mars) and 5th planet (Jupiter)
- They are large rocks that were left over after the formation of the Solar System
Every single body in space was made when clouds of gas and dust collapsed together due to the gravitational forces of attraction.
The mass of an object determines its gravitational force
Asteroids have very small masses in comparison to Jupiter. The gravitational force of Jupiter prevents lots of asteroids from joining together to form planets.
Origin of the Moon:
1) The earth’s density is about 5500kg/m3 while the moon’s density is about 3300kg/m3
2) There is NO iron on the moon
3) The moon has the same oxygen composition as earth, but meteorites from other parts of the solar system have different oxygen compositions; they must have formed from the debris of the collision
Evidence for Asteroids:
Geologists examine many crater sites to determine if they were caused by asteroids; on one such site they discovered quite a lot of the metal iridium, which is not normally found in the earth’s crust, but is common in meteorites.
Furthermore, many fossils were discovered under the layer of iridium, but very few were found above – tsunamis have disturbed these fossils, carrying some 100s of kilometres away.
A Comet’s Orbit:
Most comets will pass inside the orbit of mercury, but outside the orbit of Pluto.
Near-Earth Objects (NEOs):
Scientists are constantly monitoring and plotting the paths of comets and other near-Earth objects.
If they were to find out that an NEO was headed for Earth, they would have to explode a rocket close to the NEO which would alter its course enough to miss Earth.
Past Papers:
PPQ(1):
PPQ(2):
PPQ(3):
Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
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