Showing posts with label meteorite. Show all posts
Showing posts with label meteorite. Show all posts

August 6 - Life on Mars?????!?!!!

Posted on August 6, 2020

Meteorites are found all the time - especially in Antarctica, where the dark space stones show up well on the ice!



Scientists think that some meteorites found on the Earth originated on Mars. These meteorites are made up of elements in the same mix as rocks and air on Mars. 


You may wonder, okay, but how do rocks on Mars travel to Earth?

Most meteorites are created when something in space impacts another something - for example, when two asteroids collide, or when an asteroid hits a moon or planet - and those impacts spray rocks in all directions - some towards Earth's orbit. So it makes sense that some meteorites found on Earth are from Mars!

Okay, so we find meteorites often, and meteorites that originated on Mars sometimes...

But what about a meteorite - found on Earth - that has evidence of ancient life on Mars?

On this date in 1996, a group of scientists announced that they had found evidence for ancient microscopic life inside a Mars-originating meteorite!

Wow! That would be an absolute first - first evidence of actual life on another planet or another anything-other-than Earth.

BUT, alas, the electron microscopic photos that seemed to show fossilized bacteria could be explained in less dramatic ways. For example, the wormlike structures could just be uneven patches in the coating used to study samples with electron microscopes!


It's not certain that the meteorite (ALH 84001) does NOT have microfossils, but it's also not certain that it does. Science inches forward by testing and retesting hypotheses - which are educated guesses of how things work - and by replicating earlier work. Some scientists who work with meteorites, with Martian rocks still on Mars, and with astrobiology are trying to look for evidence of ancient Martian life, trust me! 

So even though science-in-general finds the claim about ALH 84001 premature, it's not ridiculous and might - unlikely, but might - prove to be true.


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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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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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