Showing posts with label meteor. Show all posts
Showing posts with label meteor. Show all posts

June 30 - Asteroid Day

Posted on June 30, 2020

Today is Asteroid Day, and tonight is also National Meteor Watch Day (in the U.S.). 


The two are somewhat related. Here's the deal:

The solar system formed from a dense cloud of gas and dust. It started collapsing, much of the gas and dust being pulled by gravity into the center. It started rotating as well. 



About 99.8% of the matter (the gas and dust) in the cloud ended up being pulled into the center and thus created the Sun. A fair amount of the leftover matter formed the eight planets and the various dwarf planets (aka Plutoids). A lot of the smaller bits became moons and rings - and a bunch of smaller-sized rubble that circles the Sun between Mars and Jupiter makes up the asteroid belt.



Asteroids, therefore, are leftovers in the formation of the solar system. They are defined as small rocky bodies that circle the Sun. (Moons and rings primarily circle planets or dwarf planets, and even though they also circle the Sun as their planet orbits our star, since their own orbit is around something other than the Sun, moons and particles that make up planetary rings are not considered asteroids.)

Asteroids range in size from dwarf planets like Ceres, which is about half the size of Pluto, down to grains of dust. Scientists' best guess of the number of asteroids is one to two million.

Meteors are any small rocky or metallic body of matter from outer space that enters the Earth's atmosphere. Most meteors burn up in our atmosphere because of the friction from running into so many air molecules . These are the beautiful streaks of light - often called shooting stars - that we are urged to look for tonight on National Meteor Watch Day.


Any meteor that is large enough to get all the way through the atmosphere and hit ground (or, more likely, ocean) is called a meteorite. 
When we talk about the theory that an asteroid hit the Earth and killed off the dinosaurs, we are talking about a really large meteor that formed a huge crater and probably mostly vaporized - causing an awful climate change event that resulted in lots and lots of species dying off.

And that is why Asteroid Day and National Meteor Watch Day are related. Asteroids can become meteors, and bits of asteroids that get hit by something can chip off and become meteors. The likelihood of a person or even a building being hit by a meteorite is surprisingly small; some sources say that there is only one confirmed case of a human being hit and (mildly) injured by a meteorite in all of history, but there is some evidence that it has happened at least a handful of times. 

But scientists say that a really large impact could have disastrous results, so we should watch for asteroids and other space debris that could become meteors!






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December 18 - Space! The Last Frontier!

Posted on December 18, 2019

Of course there's plenty of stuff to explore here on planet Earth - we will hopefully make more discoveries about the ocean floor, the deepest trenches, and the interior of the Earth, for example, and of course there's still TONS to learn about the complexities of living things and especially brains.

But as far as new lands to visit, explore, and maybe even settle - that we'll only find in space.


Today is the anniversary of several space-related events:

On this date in 1958, the world's first communications satellite was launched.

Called Project SCORE (Signal Communications by Orbiting Relay Equipment), it was the world's first purpose-built communications satellite, the second test of a communications relay system in space, and the first broadcast of a human voice from space. U.S. President Dwight D. Eisenhower did NOT go up in the Atlas rocket, of course (at this point in history, there had been no humans in space), but there was an on-board tape recorder that played a tape with Eisenhower's Christmas message to the world!

On this date in 1966, astronomer Richard Walker discovered another of Saturn's moons.

Back in the olden days, all our discoveries about space began from observations made on Earth. Since then we have invented space telescopes and manned and unmanned explorers that fly by or orbit or land on a moon or planet or what-have-you.  

In 1966, some of this unmanned fly-by and lander stuff had already happened, but most discoveries were still done with a telescope and photographic plates and painstaking comparison of photographs. That kind of careful comparison is how Walker discovered what is sometimes called Saturn XI - the eleventh moon of Saturn's to be discovered. ("XI" is the Roman numeral for "11.") This moon has been named Epimetheus.

Saturn's moon Epimetheus (above) is named for
one of the Titans in Greek mythology (below),
even though the resemblance is not all that striking!

On this date in 1973, the Soviet Union launched Soyuz 13.

This manned spaceflight was the Soviet Union's first mission dedicated to science. The Soyuz was especially changed in order to carry the Orion 2 Space Observatory, which collected information about stars' ultraviolet spectra.

On this date in 1999, NASA launched the Terra platform with five Earth-sensing instruments.

This launch was performed by the U.S., but the Terra platform represented scientists from around the world. The platform name was the result of a contest among high school students; Terra means "Earth" in Latin. The various instruments on Terra included infrared sensors that create high resolution images of ice, clouds, and land surfaces; instruments that took spectral readings; and instruments that measured and tracked pollution. Data collected from Terra help scientists understand climate change, the way pollution spreads, and trends in aerosol and carbon monoxide pollution.

On this date in 2018, a meteor exploded over the Bering Sea. 
The explosion was 10 times greater than the atomic bomb that destroyed Hiroshima. Luckily, this meteor exploded 16 miles above a sea rather than right on a city! - and so nobody even noticed...
We were just talking about the instruments on the Terra platform (see above), and it turns out that the only reason we know about this 2018 explosion is because one of Terra's instruments captured an image of the meteor's remnant and its dark trail of smoke just a few minutes after the explosion. The white background is the surface of the clouds above the sea.
The brown diagonal streak near the center
of the photo is the meteor fragment
that was caught on camera.



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October 27 – Meteor!

Posted October 27, 2018

A lot of debris from space falls onto the Earth.

And when I say "debris," I MOSTLY do not mean human trash / junk. Space junk like lost equipment, dead satellites, and upper stage boosters is definitely a concern, but most of it is circling the Earth; stuff that gets bumped out of orbit and falls on us often burns up in the atmosphere. Of course, some larger pieces do survive the friction of plunging through our protective layer of air, and NASA claims that an average of one catalogued piece of debris falls somewhere on Earth each day - and has for 50 years now!


But....so far there has been zero big-time problems for people down on Earth from the human-made debris. No significant property damage, no deaths or injuries.

But in space, there is a lot of debris that humans didn't make. I'm talking about all the dust, bits of rock, pebbles, larger chunks of rock and ice, and even boulders or small planetoids. All of this debris is either stuff left over from when the solar system formed or stuff created when comets break up or when rocky or icy bodies collide in space. 









 
And any of that dust-to-boulder-or-larger stuff that happens to hit the Earth becomes a meteor (a "shooting star") in our skies - lovely streaks of light that are exciting to see.

Rarely does a meteor make it all the way to the Earth's surface, but the larger bits that do are called meteorites. There are meteorites that are mostly made of iron, some that are mostly made of stone, and some that are a mix of stone and iron.





Now - how many meteors and meteorites fall on the Earth? An astounding 37,000 to 78,000 TONS of space debris rains down on Earth EVERY YEAR!

Most of that would come from dust-sized particles that of course burn up in the atmosphere. Phew!

Still, thousands of teeny bits of space rock make it all the way to the Earth's surface every year. Of course, most of them fall into the ocean (which makes up about 70% of the Earth's surface), and a lot of them fall onto empty sweeps of land like Antarctica, Siberia, the Sahara Desert, the forests of Canada and Africa and South America, and so on... 

Most of the Earth is ocean.
Above, the Pacific Ocean as viewed from space.
Below, even the land portions of the Earth are
only partially inhabited.


On this date in 1973, a 3-pound (1.4 kg) meteorite struck the ground in a city - in Cañon City, Colorado, to be specific - a very rare event. It landed on a garage, tearing a 6-inch hole in the garage roof, and leaving a 2-inch gash in the cement floor.


Notice that it didn't hit a car, or a pet, or a person.

In all of history, apparently, only 35 meteorites have ever hit a human-made structure in the United States. And only one person has ever been hit by a meteorite (at least that we know about): a 34-year-old woman napping in her home in Alabama was struck by a nine-pound meteorite. It gave her a big bruise but that was it! Wow!

This "only one person" I'm talking about is the only person known to have been hit by a meteorite anywhere in the world, throughout all of recorded history. (A man in India who was reported to have died in 2016 from an impact of what many presumed was a meteorite was apparently the victim of some sort of land-based explosion.)

However, being hit by a meteorite isn't the only thing to worry about. A really large meteorite can explode in the atmosphere and create a shock wave. In 2013 a 12-ton meteor entered the Earth's atmosphere and broke apart some 20 miles (30 km) above the Russian city of Chelyabinsk. About 1,000 to 1,200 people were injured in that extremely rare incident - but most of the injuries were cuts from glass broken by the shock wave.

I couldn't find any evidence that bits of the meteorite itself struck anyone. I read that 75% of the meteorite evaporated, but 9,000 to 13,000 pounds of meteorite (in varying sizes of chunks) fell onto Earth. The largest fragment was 1,400 pounds, and it broke through ice that was more than two feet thick to fall into a lake, leaving a 23-foot-wide hole in the ice!


But apparently no pets or people were struck by meteorite pieces - and nobody died from their shock-wave injuries. Phew!




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