P2g: Threats to Earth Flashcards
How was the moon formed(3)
collision between 2 planets (Earth and Mars-size object) billions of years ago
their dense iron cores melted and merged to form the core of the Earth
less dense material were ejected and orbitted around Earth for a while and eventually came together (due to gravity) to form moon
Evidence for the Earth-Moon system as the result of a collision between two planets (3)
Moon has lower density than Earth
Moon doesn’t have a big iron core like Earth does
Moon has the same oxygen composition as the Earth, but rocks on Mars and meteorites from other parts of the Solar system have different oxygen compositions
Describe asteroids(3)
lumps of rock in orbit around the sun that are too small to be planets
left over from the formation of the Solar System
in orbit between Mars and Jupiter
Evidence for past asteroid collisions (2)
layers of unusual elements in rocks - must have been imported by asteroid
sudden changes in fossil numbers between adjacent layers of rock , as species suffer extinction
Explain why the asteroid belt is between Mars and Jupiter
during formation of Solar System, rocks between Mars and Jupiter didn’t form planet as large gravitational attraction of Jupiter (due to large mass) kept interfering, breaking up clusters of asteroids which would otherwise have eventually formed a planet
Describe comets(5)
made from rock, ice and dust
tail formed from a trail of gas and debris as its ice melts as it approaches the Sun
-Tail points away from the Sun as a result
have highly elliptical orbits
come from objects orbiting the Sun far beyond the planets
How does the speed of a comet change as it approaches a star?
comets speed up as they approach the Sun, because the Sun’s gravitational pull increases as it gets closer, making it speed up
What are observations of NEOs used to do
to determine their trajectories by calculating it
Why is it difficult to observe NEOs?
they are small, dark and may have unusual orbits
Possible actions which could be taken to reduce the threat of NEOs (2)
surveys by telescope or monitoring by satellites to detect NEOs while they are still far away from Earth and check if their trajectories are directed at us
deflect them using powerful explosions when they are distant enough from Earth if they are on a collision course with Earth
