METEORS, ASTEROIDS and COMETS

Tahoma Jr. High8th Grade ScienceMaple Valley, WA

Meteoroids, asteroids and comets are all basically “leftovers” from solar system formation.

METEORS: small rocks flying through Earth’s atmosphere

Most are sand grain sized and easily burn up before reaching the ground…if they hit the ground they are now called a “meteorite”.

ASTEROIDS: big space rocks

In 2036 Apophis (a 350m asteroid) will pass within 22,000 miles from Earth.That is BELOW satellite altitude!

The problem with spotting asteroids and meteoroids (meteors out in space) is they are small and don’t reflect much light.

Many pass by Earth before we even see them!! (they come out of the Sun).

08 NOV 2011 an asteroid, called 2005 YU55, about the same size as Apophis (~aircraft carrier size) zipped by the Earth inside the Moon’s orbit – a very, very close call.

If it hit Earth, it could easily wipe out a city.

The last time something this size came this close to us it was 1976 – and the next time (as far as we know!) will not be until 2028. Without many astronomers looking for these – and we don’t have many people looking in the Southern Hemisphere -

an impact will likely be a complete surprise.

Most of the asteroids are in the Asteroid Belt – but not all of them – many are also out in the Kuiper Belt.

There are many objects beyond Neptune out in the Kuiper Belt – 1,200 discovered thus far – four similar to Pluto in

size (planetoids) – but most will be smaller, like asteroids.

COMETS: dirty snowballs

Tail always points away from the Sun – and comet gets smaller after each pass

Comets can also be found in the Kuiper Belt just beyond Pluto. These “short-period” comets may also contain organic chemicals (the “stuff of life”) and have regular, predictable orbits.

This is Halley’s comet in 1985, it will not be back for another 76 years, but is a short-period comet (<200yrs).

“Long-period” comets come from a much further place called the Oort Cloud (some 2LY away!) and usually do not fall in towards the Sun. They are very unpredictable and can come from any direction. Some scientists speculate that mass extinctions, such as one 35 million years ago, may be due to nearby supernovas disturbing Oort Cloud objects to fall towards the Sun.

In any case, long-periodcomets can be quitespectacular, like Hale-Boppwhich appeared in 1997 butwon’t return for 2,380 years!

          

                    

Project “Stardust” was launched in 1999, and in JAN 2004 made a close fly-by of comet Wild-2 and caught some of its tail particles (luckily there was more than one layer of shielding!) and brought them back to Earth in JAN 2006to learn more about thesolar system’s birth.It was the first missionof its kind.

Here’s videotaken fromthe 240 kmfly-by.

Because of the “out-gassing” jets of comets (or passing close to a planet), they can change their orbits - bringing them close to other planets and possibly being ripped apart and then crashing into them.

Here’s Shoemaker-Levy 9’s “string of pearls” hitting Jupiter in 1994.

Just ONE of these fragments had the energy of over 600 times the world’s arsenal of weapons!!

After about 500 passes close to the Sun the ice of a comet will be vaporized away leaving a meteoroid-like body. Close encounters with other bodies will cause either an impact or be ejected from the solar system.

Impacts from asteroids and comets are a definite threat to life on Earth – and have played a significant role in Earth’s history.

In June 2002 a 100m(100yd) meteor camewithin 1/3 the distanceto the Moon(a VERY near miss!).

Here’s what only 40m would do. Barringer Crater, Arizonahit 50,000 years ago

Here’s other impact craters that are harder to see because of erosion.

Australia –300,000 years old

Canada –212 million years old

Africa –1.3 million years old

Mexico (special radar looking under soil and water)65 million years old

Canada (a pair hit at the same time – a piece having broken off just before impact) 290 million years old

In FEB 2013, a rock “only” 17m (53’) wide hit the atmosphere at 65,000 km/h (40,000 MPH) in Russia and broke apart in the lower

atmosphere exploding with the force of 30-40 “small” atomic bombs similar to those used on Japan. It’s the biggest “space caused explosion” in 100 years, when a 40m wide one hit the same area of the world and flattened over 800 square miles of

forest. Over 1,000 people were injured by the 2013 blast – most had their ears damaged by the shock – or were cut by falling glass

from all the windows blown out.

piece landed on frozen lake and melted through

Meteor showers can be quite spectacular, and happen when Earth passes through a debris field like those left by a comet.

Meteors are small rocks and are usually sand grain sized and burn up in the atmosphere.

Regardless, it is important that we investigate possible impacts as we are often surprised to find objects that have ALREADY passed Earth since they came from the Sun’s direction and we couldn’t see them until they were headed away!

There are programs underway,such as SpaceGuard, that lookfor 1km sized objects but itcosts a lot of money andtakes a lot of time to find allthese objects, and even a smallone that’s harder to see can doMUCH damage.

In 2014, one named “The Beast”, luckily missed us by “only” 3x the distance of the Moon (pretty close).

This one was 10x bigger than the one in Russia – the size of a football stadium! (easily a “city killer”).

31,000MPH – lots of energy. Problem: it wasn’t discovered until 2 weeks before passing by Earth.

from 12 AUG 2009:http://www.telegraph.co.uk/science/space/6016787/Nasa-short-of-money-to-watch-asteroids-heading-to-Earth.html

However, the academy concluded that there had been "relatively little effort" by the US government to addressing the threat.

NASA calculated that to spot the asteroids as required by law would cost about $800 million between now and 2020, either with a new ground-based telescope or a space observation system.

At the moment, NASA has identified about five near-Earth objects that pose greater than a one-in-a-million risk of hitting the planet and being big enough to cause serious damage.

Astronomers are watching a 430-feet diameter rock that has a 1-in-3,000 chance of hitting Earth in 2048 and a much-talked about asteroid, Apophis, which is twice that size and has a 1-in-43,000 chance of hitting in 2036, 2037 or 2069.

from 28 FEB 2012:http://abcnews.go.com/Technology/asteroid-threat-2011-ag5-close-earth-2040-scientists/story?id=15809386

Now we have a newer possible threat discovered in 2011 – but we had such a quick look at it we couldn’t quite plot its orbit very accurately. However, it seems that it will at least pass very close to Earth in 2040 and may be on a collision course. Only further observations/measurements will determine how close it will come. This asteroid, 2011 AG5, is 150m (450’) wide – meaning if it hits Earth, it will cause quite a lot of destruction no matter where it hits.

Let’s hope it’s just a near miss,like many others have been.

Chances of impacts and their energy.

Dia(m)

Yield (megatons)

Interval(years)

Consequences

< 50 < 10 < 1meteors in upper atmosphere most don't reach surface

75 10 - 100 1000 irons make craters like Meteor Crater; stones produce airbursts like Tunguska; land impacts destroy area size of city

160 100 - 1000 5000 Iron stones hit ground; comets produce airbursts; land impacts destroy area size of large urban area (New York, Tokyo)

350 1000 - 10,000

15,000 land impacts destroy area size of small state; ocean impact produces mild tsunamis

700 10,000 - 100,000

63,000 land impacts destroy area size of moderate state (Virginia); ocean impact makes big tsunamis

1700 100,000 - 1,000,000

250,000 land impact raises dust with global implication; destroys area size of large state (California, France)

1 megaton would be 77x the bomb dropped on Hiroshima, Japan in WWII

WHAT IF AN ASTEROIDWERE HEADED TOWARDS EARTH?

WHAT COULD HUMANS DO TODAY TO PREVENT IT FROM HITTING EARTH - BECAUSE IT’S NOT A MATTER OF “IF” –

BUT REALLY “WHEN” ?!!?

COLLISIONS VIDEO FIRST - BUT OPTIONAL IF TIME: your table group will look at various impact

simulations and games.

Keep in mind the REALITY OF THIS HAPPENING IS REAL – it is not just a game. It has happened before,

and WILL happen again. Will we be able to do something about it? It will depend on how much

early warning we get and how big it is.end show