Lecture 3 - Space Hazards

Question 1

What generates Earth’s magnetic field?

Answer 1

Convective flow of electrically-conducting liquid iron in the
outer core is organized into spinning columns by Earth’s rotation.

Question 2

What is the magnetosphere?

Answer 2

A region of space surrounding Earth in into which Earth’s magnetic field lines extend.

Question 3

What is solar wind?

Answer 3

An energetic stream of charged particles (mostly electrons and protons) that flow out from the Sun across the solar system at speeds as high as 900 km/s.

Question 4

How long does it take solar wind to reach earth?

Answer 4

2-5 days

Question 5

What happens when solar wind reaches earth?

Answer 5

The magnetosphere deflects most of it from impacting Earth.

Question 6

How are the aurora created?

Answer 6

Disturbances to the geomagnetic field from solar wind induce electric currents in the ionosphere, especially at high latitudes. These electric currents are the aurora.

Question 7

Why does Mars lack a thick atmosphere?

Answer 7

We suspect that its outer core has solidified so there is no convection and therefore no magnetic field. This means that solar wind was able to strip away its atmosphere.

Question 8

What is a Coronal Mass Ejection?

Answer 8

A larger release of energetic particles from the sun.

Question 9

When do sunspots generally occur?

Answer 9

Before a coronal mass ejection. Sunspots are on an 11 year cycle.

Question 10

What was the Carrington event?

Answer 10

A huge coronal mass ejection and a powerful geomagnetic storm on 1-2 September 1859. Telegraph systems in Europe and North America failed, giving their operators electric shocks and setting their offices on fire. The northern lights were seen almost as far south as the equator.

Question 11

What happened on the 13th of March 1989 in Quebec?

Answer 11

There was an electrical power blackout three days after astronomers witnessed a huge coronal mass ejection on the Sun. The aurora could be seen as far south as Florida.

Question 12

What would be the cost of a Carrington scale event today?

Answer 12

around 40 billion dollars per day in the US alone

Question 13

What impacts a place’s tendency for geomagnetic storms?

Answer 13

geology

latitude

Question 14

What are impact events?

Answer 14

Collisions of extraterrestrial asteriods, comets, or their fragments, with Earth.

Question 15

What are asteroids?

Answer 15

They are stony or metallic bodies orbiting the Sun, mostly in the Asteroid Belt between Mars & Jupiter or the Kuiper Belt beyond Neptune. Collisions can bump asteroids into orbits that intersect Earth’s.
Asteroid belt objects vary from 100s of meters to 100s of km in diameter.

Question 16

What are the largest asteroids?

Answer 16

Ceres ~950 km in diameter

Vesta ~525 km in diameter

Question 17

What are comets?

Answer 17

They are 0.1–60 km bodies composed of rock, dust and ice (frozen water, methane, ammonia etc.). Most originate from the Kuiper Belt or the distant Oort Cloud and orbit the Sun in highly elliptical orbits.

Question 18

Why do comets appear to have “tails”?

Answer 18

When in the inner solar system, solar radiation vaporises volatiles in the comet nucleus, which stream away from the comet as a tail (points away from the Sun).

Question 19

What is a meteor?

Answer 19

When asteroids, comets or meteoroids or their fragments enter the atmosphere they produce a meteor.

Question 20

What is a meteorite?

Answer 20

When asteroids, comets, meteors, meteoroids or their fragments enter the atmosphere and survive passage through the atmosphere to impact Earth, they produce a meteorite.

Question 21

What is most likely to survive passage through the atmosphere and impact the surface of earth?

Answer 21

Asteroids (>1 m)

Question 22

What normally burns up in the atmosphere and rarely produces meteorites?

Answer 22

Meteoroids (1 mm–1 m)

Question 23

What happened on the 15th of February 2013 in Chelyabinsk, Russia?

Answer 23

A meteor was observed. It exploded in a damaging air burst before it could reach the surface.

Question 24

What was observed over Siberia on the 30th of June 1908?

Answer 24

A massive fireball was observed, followed by an explosion that was heard 1000 km away. People 480 km away were knocked off their feet.

Question 25

What did a 1927 expedition discover about the 1908 fireball?

Answer 25

They found 2,000 km² of flattened trees, with many charred on one side.
No impact crater was found - the meteor exploded a few kilometres above the surface. It was likely ~50 m in diameter.

Question 26

What is capable of producing impact craters?

Answer 26

Asteroids >50-100 m diameter

These occur on average every few thousand years

Question 27

What does impact energy depend on?

Answer 27

the impactor size and speed

Question 28

What are simple impact craters?

Answer 28

created by smaller and/or slower impactors

they have raised rims and bowl-shaped central cavities

Question 29

What are complex impact craters?

Answer 29

created by larger, faster impacts
they have ring structures from gravitational collapse of crater walls and central peaks from rebound of the compressed crater floor

Question 30

What factors indicate an impact site on Yucatan Peninsula?

Answer 30

distribution of melted rock globules
shocked quartz
tsunami deposits

Question 31

Why is the Chicxulub crater on the Yucatan Peninsula significant?

Answer 31

It is believed to be the crater from the meteorite that caused the extinction of the dinosaurs.

Question 32

How many confirmed impact craters are there worldwide?

Answer 32

~190, including ~60 in North America

Question 33

Which two mass extinctions are believed to have been caused by meteorites?

Answer 33

End of Cretaceous

Late Devonian