DON'T PANIC!

I hope you found those to be nice, friendly letters.

At any rate, truly, there is no need to panic.  Friday will come and go, and we will NOT be destroyed by a giant rock from space.  Truly, we won't.

You've probably heard about asteroid 2012 DA 14 (yes, that's really the only name it has!), which will be making an extraordinary pass by Earth this Friday.  In fact, here's the official details:

Asteroid: 2012 DA 14
Date: Friday, February 15, 2013
Time: 2:24PM EST
Distance at closest approach: 17,200 mi from Earth
Size of asteroid: 164 ft. wide
Composition: Stone
Chance of impact: ZERO

Did you read that last bit?  There is a ZERO chance that 2012 DA 14 will hit the Earth this Friday.  Zero. Zilch.  Nada.  None.  No chance at all.  Not even if it happens to hit a satellite (which is terrifically unlikely) - it cannot possibly "bounce" off a satellite and hit the Earth.  It simply will not happen.

So, what will happen?

This asteroid will zip past our planet a bit inside the orbit of the geosynchronous satellites.  Those satellites handle things like weather and communications, among others.  The rock will go outside the GPS satellites, however.  So while it will be close to us...it won't be that close to us. 

Some folks are hoping to be able to see this rock as it zips past.  That will be extremely difficult, for several reasons.  First of all, it will be moving a good clip...17,400 mph, in fact.  That means it will move across the sky about 1 degree per minute - tough to track, that's for sure.  And you'll need to track it, because it won't be visible to the unaided eye.  Even coming so close, the rock is so small, you'll need at least a pair of binoculars to see it at all.  And one other small problem...you'll need to be in the middle of the Indian Ocean.  Sumatra will get a nice view.  So...not much of an event here in the U.S.

But now, let's tackle the juicier question...what if the scientists are wrong? (They're not.)  What if it does hit us after all?  (It won't.)

Okay, let's consider it.  What would happen if 2012 DA 14 hit the Earth?  Lucky for us, we've got some good models for that...because they've already happened.  (insert gasp of surprise here)

2012 DA 14 is about the same size as the asteroid that impacted the U.S. some 50,000 years ago just outside of what is today Winslow Arizona.  That meteor struck the ground and blasted a hole in the Earth 4,000 feet in diameter, and 570 feet deep.  You can visit the crater today - it's called Barringer Meteor Crater.  

Barringer Meteor Crater in Arizona

Now, the meteor that created Barringer Meteor Crater was made largely of iron.  2012 DA 14 is a stony object.  So it would not impact with nearly the same amount of force.  In fact, it probably would not impact at all...the stress of enter Earth's atmosphere at a high rate of speed would likely shatter the rock before it ever made it to the ground.  We've got a model for that too.  On June 30, 1908, a meteor about the size of 2012 DA 14 exploded over the Podkamennaya Tunguska River in Siberia.  The blast leveled 830 square miles of forest, and likely measured 5.0 on the Richter scale.  The energy of the blast was about 1,000 times as much as that from the atomic bomb dropped on Hiroshima by the United States.  If a blast like this occurred over a major population center, the results would most certainly be unpleasant.  But not Earth destroying, by any means.

Trees leveled by the Tunguska explosion in 1908.

 
So...long story short....Friday will be a great day for scientists who study asteroids...and maybe even for a few amateurs who can get photographs of our celestial visitor...but for most of us, it will simply be another day on planet Earth.

Until the next close shave...
Carpe noctem!
Kelly

Smoke on the Water and Fire in the Sky

Well, I don't know about the smoke on the water part, but last Sunday in Nevada and California there was definitely some fire in the sky.

It's now fairly certain that the explosion reported by so many folks in those two states was a bolide, or a fireball.  Fireballs are large meteors that are generally very bright, and are usually accompanied by a good deal of noise.  Most often they explode in the air - a result of the stress of passing through the Earth's atmosphere.  But what is a bolide, really?

Simply put, it's a shooting star.  A very impressive one.

Shooting stars are not actually stars.  They are meteors - rocks from space which enter the Earth's atmosphere.  Most are extremely tiny - like grains of sand or dust.  The friction caused by all that air rubbing against the rock actually makes the air glow - that's the streak of light we see and call a shooting star.  Tiny dust-fragments never get that far - they disintegrate and are gone before they can heat up enough air for us to see.  Larger chunks make a distinct streak of light, but they actually don't make it very far into our atmosphere either before they too are destroyed.  Big chunks, though, can do some amazing things.

A map showing the location of the April 22nd fireball.  Courtesy spaceweather.com

The fireball this weekend was clearly seen in daylight.  When the meteor finally burst apart from the stress, it was pretty close to the ground - maybe about 5 miles up.  If it had been higher up, there would not have been so many reports of loud booms.  Based on information gathered from eye witnesses, it's likely that the meteor which caused all the excitement was about the size of a minivan when it entered the atmosphere.  The energy of the explosion has been estimated at about 3.8 kilotons of TNT, so this was a pretty big deal.  Since it exploded above the ground, there was little actual damage, but it's possible some pieces of the meteor may now rest on the ground.  If these meteorites can be found, they would be quite special, as it is rare to be able to so accurately pinpoint the event that a meteorite came from.

A picture of the Nevada/California fireball of April 22.  Credit: Lisa Warren

So don't forget to keep looking up, even in daylight.  You never know just what you might see!
Carpe noctem et diem!
Kelly

Over the Moon

Actually, I'm kind of not.

We had an amazing night last Saturday, observing the Moon.  The NASA exhibit was awesome...I touched a piece of the Moon!  Our Moon is incredible!

And that got me thinking...what about all the other moons?  Does anybody realize how incredibly awesome they are?

We tend to focus on our own Moon.  Makes sense...it's big, bright, and plays an important role in the existence of life here on Earth.  But among the major planets there are 168 other moons...all equally fascinating worlds in their own right!  So let's explore some of the other moons out there...and kind of play a little compare and contrast with our Moon, if you will.

Earth has one moon.  That's it...just The Moon.  Most of the other planets have many more moons indeed...Jupiter takes the prize for the most (if you don't count ring particles!) at 64 known satellites.  Even Mars has 2 moons - double what we've got!  The only planets with fewer moons than Earth are Mercury and Venus - neither world has any moons at all. 

Size matters though...Mars' two moons are extraordinarily tiny.  Phobos (Fear) and Deimos (Panic), as the Martian moons are named, are most likely captured asteroids.  They are small potato-shaped bodies, barely findable in a telescope from here on Earth...and even then only when Mars makes a close approach to us.  Such jagged chunks of stuff can be found orbiting all of the gas giant planets as well...the majority of the solar system's moons are weird little lumpy leftovers from the formation of the planets.

Phobos (top) and Deimos (bottom).  Courtesy NASA.

On the other hand, our Moon is not the largest in the solar system, either.  That distinction goes to Ganymede, largest moon of Jupiter.  In fact, Ganymede is larger than the smallest major planet...at 3,280 miles across it beats Mercury's size by more than 200 miles.  This massive moon is truly a world in its own right...it shows evidence of tectonic activity, its own magnetic field, and it might even have an atmosphere.  Talk about your colossal moon!

Ganymede from the Galileo spacecraft.  Courtesy NASA.

Speaking of atmosphere, our Moon hasn't got one.  If you plan on visiting the Moon, make sure you bring your own air.  The moon with the densest atmosphere?  Saturn's enigmatic Titan.  The moon, explored by the Huygens lander, has the distinction of being the only moon known with an atmosphere consisting of more than trace gases.  It is a dense soup of hydrocarbons, with numerous distinct layers...shrouding the moon and looking like a heavy layer of orange smog.  So impressive is this moon's atmosphere that it is believed to be, like Venus, a super-rotator - that is, the atmosphere actually rotates much faster than the moon itself does.  The Huygens probe showed us incredible details about Titan, but so much more remains to be learned.

Titan from the Cassini spacecraft.  Courtesy NASA.

The surface of Titan from the Huygens probe.  Courtesy NASA/ESA.

Keep in mind, we've limited ourselves at this point to explore the moons of the major planets.  There are more moons than that in the solar system!  Of the 5 confirmed dwarf planets, 3 have moons: Eris has Dysnomia, Haumea has Namaka and Hi'iaka, and Pluto has Charon, Hydra, Nix, and the newly discovered P4 (it's so new it doesn't have a name yet!).  Pluto is only 2/3rds the size of our Moon - and it has 4 moons of its own!  Incredible!

Pluto and its 4 moons from the Hubble Space Telescope.  Courtesy NASA.

Oh, so you think only planets, be they major or dwarf, can have moons?  Not so...the asteroid Ida has a moon, Dactyl, first discovered by the Galileo spacecraft as it passed by on its way to Jupiter.  The solar system is rich with moons!  Take some time to explore them...both by reading up on them and by checking them out through telescopes - the moons of Jupiter and Saturn can easily be seen in telescopes from Earth!

Ida and its tiny moon Dactyl from the Galileo spacecraft.  Courtesy NASA.

Have fun mooning around, and I'll see you next time!
Carpe noctem,
Kelly