Starship Asterisk*

by **William Roeder** » Mon Feb 04, 2008 9:00 pm

Arramon wrote: Those Chinese better be sending images of the darkside of the Moon when its in the light of the Sun so we can all see! =)

Why would the darkside ever be lit? You meant farside, there is no darkside except in the force

by **neufer** » Mon Feb 04, 2008 8:55 pm

Arramon wrote:If an asteroid miles upon miles wide hit the Moon... oi! Possibly shattering it or breaking large chunks off. Light side, dark side, no matter. This entire region of space would be awash in the afterglow. But how large would the object need to be to cause such an event? And can scientists tell what the largest object may have been so far from the size of the craters upon the Moon's surface?

http://www.solarviews.com/eng/tercrate.htm
It seems to be a general rule of thumb that:
15 x Diameter of meteor ~ Diameter of crater

So the biggest "craters" observed today are caused
by (~4 billion year old) ~150km sized meteors:
---------------------------------------------------
http://en.wikipedia.org/wiki/South_Pole-Aitken_basin

<<The South Pole-Aitken basin is an impact crater on Earth's Moon. Roughly 2500 kilometers in diameter and 13 kilometers deep, it is the largest known impact crater not only on the Moon, but also in the entire solar system. >>
---------------------------------------------------
http://en.wikipedia.org/wiki/Hellas_Planitia

<<With a diameter of about 2,300 km (1,400 mi), [Hellas Planitia] is the largest impact structure on Mars. The altitude difference between the rim and the bottom is ~9 km (30,000 ft). If all the material excavated from it were spread evenly on the continental United States, there would be a 3.5 km (12,000 ft) thick layer of debris. The basin is thought to have been formed during the Late Heavy Bombardment period of the Solar System, over 3.9 billion years ago, when a large asteroid hit the surface.>>
---------------------------------------------------
http://tinyurl.com/3exxpy

<<This image shows details of [Mercury's] Caloris basin, one of the largest impact basins in the solar system. MESSENGER's images indicate that the basin rim, shown as a blue dotted line in the image, is [about] 1550 kilometers in diameter.>>
---------------------------------------------------

by **Arramon** » Mon Feb 04, 2008 6:52 pm

"...an object of such great size that when it struck the Moon, ALL upon Earth would know and feel its impact."

Not human-, car-, or even baseball-sized meteors... but something catastrophic in size.

Of course, this hasn't happened in our time as humans, because we've all known the Moon as it's been for as long as our human eyes have been able to peer up, and it's still in one piece.

If an asteroid miles upon miles wide hit the Moon... oi! Possibly shattering it or breaking large chunks off. Light side, dark side, no matter. This entire region of space would be awash in the afterglow. But how large would the object need to be to cause such an event? And can scientists tell what the largest object may have been so far from the size of the craters upon the Moon's surface?

Those Chinese better be sending images of the darkside of the Moon when its in the light of the Sun so we can all see! =)

by **Ace** » Mon Feb 04, 2008 12:57 am

here's another version I did if anyone wants to look at it:

http://www.4shared.com/file/36790326/75 ... nbank.html

it's better but a bit smaller. The crater on the left is more clear in this one. The smaller image in the pic would be roughly the size of the original i'm guessing. That's around the point where the pixelation goes away, at least to my eyes.

by **Ace** » Mon Feb 04, 2008 12:23 am

Yes, it can work ok. I've done it a few times with other images. The pixelated image was made by zooming in several times using the zoom tool in a photo editor which results in a pixelated photo. I assume they did that because the original unpixelated photo is so tiny to look at. They should just use the resize option like I did. It results in a better and more useful image as you can see here. Pixelated images like this one are pretty useless as far as i'm concerned.

by **iampete** » Sat Feb 02, 2008 7:01 am

Ace wrote:
Ace wrote: . . . resized it down in Photoshop to the point where it wasn't pixelated, which was very small, and then enlarged it. . .

That's interesting. I was not aware that technique would yield such an aesthetic improvement even though it results in degradation of data.

Were there any pictures taken of this asteroid nearer the visible spectrum during the closest approach? I'd be interested to see a comparison of such a picture with the results of the smoothing performed by Ace.

by **Ace** » Sat Feb 02, 2008 6:39 am

Ace wrote:I hate pixelated images so I smoothed out the photo of Asteroid 2007 TU24 if anyone's interested.

In case anyone's curious about what I did to the pic, I just resized it down in Photoshop to the point where it wasn't pixelated, which was very small, and then enlarged it. You can get some good results by doing that with pixelated images. They won't be perfect since upsizing makes them blurry and all but they can come out good enough to see what the object looks like anyway.

by **neufer** » Fri Feb 01, 2008 3:20 am

NoelC wrote:Imagine aligning an image with, say, 500 meters per pixel resolution with a similar image from years gone by and blinking back and forth to see if there have been changes. Astronomers do this all the time with deep space imagery, but I've not heard of it being done with images of the Moon. -Noel

It might be worth trying but it's unlikely to succeed since
meteor craters this large are currently being generated on the
near side of the moon only about once every 50,000 years:
---------------------------------
There are only 5 known large meteor craters
on earth generated in the last 100,000 years:
---------------------------------
http://www.unb.ca/passc/ImpactDatabase/

Code: Select all

km    Crater
...........................
4.5    Rio Cuarto, Argentina  
1.9    Tenoumer, Mauritania
1.83   Lonar, India  
1.186  Barringer Arizona
0.45   Amguid Algeria

[/b]
Let's assume there are 11 other recent large
earth meteor craters still unaccounted for.
------------------------------
Now the known land area of the earth is 149 million km²
but the area of the near side of the moon
is almost 8 times smaller: 19 million km² .

Hence, compared to 16 recent large earth meteor craters there
should be only 2 recent large craters on the near side of the moon.

A moon crater of 500 meters or larger probably
happens (now a days) only once every 50,000 years.

(If only we had good photos of the
moon from 50,000 years ago.)
http://tinyurl.com/83y6n

by **NoelC** » Fri Feb 01, 2008 12:36 am

Imagine aligning an image with, say, 500 meters per pixel resolution with a similar image from years gone by and blinking back and forth to see if there have been changes. Astronomers do this all the time with deep space imagery, but I've not heard of it being done with images of the Moon.

-Noel

by **Chris Peterson** » Thu Jan 31, 2008 5:03 pm

neufer wrote:Surely if magnitude 7 impacts are observed regularly today then larger lunar impacts must have been witnessed visually in the past
but if such events were ever recorded then no record survives that we know about.

That's an interesting thing to consider. Impacts large enough to cause an easily visible flash are going to be very uncommon- probably separated by thousands of years on average. And the flashes would be brief. So it may well be that no human has ever witnessed a lunar meteor impact naked eye. But as you point out, if no record exists, it is hard ever to know for sure. I suppose, however, that as we continue to map the Moon in ever finer detail, we'll at least know if any impacts occurred in historical times that might have been witnessed.

by **neufer** » Thu Jan 31, 2008 4:48 pm

Chris Peterson wrote:
neufer wrote: <<Five monks from Canterbury reported to the abbey's chronicler, Gervase, that shortly after sunset on June 18, 1178, they saw two horns of light on the shaded part of the moon:
"This year, on the evening of June 18, when the moon, a slim crescent,
first became visible, a marvelous phenomenon was seen by several men
who were watching it. Suddenly the upper horn of the crescent was split
in two. From the midpoint of the division a flaming torch sprang up,
spewing out over a considerable distance fire, hot coals and sparks.
The body of the moon which was below writhed like a wounded snake.
This happened a dozen times or more, and when the moon returned to
normal, the whole crescent took on a blackish appearance."
The monks' observation took place during the Taurid meteor shower.
As interesting as this story is, it has been largely discredited. There are no other reports of it, although other reports would be expected. There are no reports of huge meteor storms in the following days, although such storms would certainly be produced. Images from Clementine show that while crater Giordano Bruno is young, it is almost certainly older than 800 years. And the whole issue with the Taurids is a red herring, as there's no indication that any Taurid debris is large enough to produce a 22 km diameter crater.

The Gervase story rings true a an observation of a Taurid meteor fireball BETWEEN the moon and Canterbury (as a full reading of my post would suggest).

Chris Peterson wrote:While meteor impacts are easily, and somewhat commonly, recorded on the Moon with cameras, there remains no real evidence that such an impact has ever been witnessed visually.

Surely if magnitude 7 impacts are observed regularly today then larger lunar impacts must have been witnessed visually in the past
but if such events were ever recorded then no record survives that we know about.

by **Chris Peterson** » Thu Jan 31, 2008 4:11 pm

neufer wrote: <<Five monks from Canterbury reported to the abbey's chronicler, Gervase, that shortly after sunset on June 18, 1178, they saw two horns of light on the shaded part of the moon:
"This year, on the evening of June 18, when the moon, a slim crescent,
first became visible, a marvelous phenomenon was seen by several men
who were watching it. Suddenly the upper horn of the crescent was split
in two. From the midpoint of the division a flaming torch sprang up,
spewing out over a considerable distance fire, hot coals and sparks.
The body of the moon which was below writhed like a wounded snake.
This happened a dozen times or more, and when the moon returned to
normal, the whole crescent took on a blackish appearance."
The monks' observation took place during the Taurid meteor shower.

As interesting as this story is, it has been largely discredited. There are no other reports of it, although other reports would be expected. There are no reports of huge meteor storms in the following days, although such storms would certainly be produced. Images from Clementine show that while crater Giordano Bruno is young, it is almost certainly older than 800 years. And the whole issue with the Taurids is a red herring, as there's no indication that any Taurid debris is large enough to produce a 22 km diameter crater.

While meteor impacts are easily, and somewhat commonly, recorded on the Moon with cameras, there remains no real evidence that such an impact has ever been witnessed visually.

by **Nancy D** » Thu Jan 31, 2008 4:09 pm

Here are some articles from Science@NASA about them observing objects hitting the moon.

http://science.nasa.gov/headlines/y2006 ... oradic.htm

http://science.nasa.gov/headlines/y2001/ast30nov_1.htm

http://science.nasa.gov/headlines/y2005 ... taurid.htm

If you go to their main page http://science.nasa.gov/ and just do a search for the word moon you get a lot of interesting articles.

by **neufer** » Thu Jan 31, 2008 3:29 pm

npsguy wrote:
Arramon wrote:good ol' asteroids..

I'm just waiting for something to hit the moon... wake up the entire world about how little we can do concerning these objects that are everywhere in the solar system. Anyone know the last time something actually struck the moon and was recorded
Yep November 2005
http://www.astronomy.com/asy/default.aspx?c=a&id=3794
A meteoroid struck the Moon in early November, and NASA scientists caught the impact on tape. NASA scientists at the Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Alabama, set up a telescope outside their office building to monitor flashes on the Moon's shadowed side... According to Bill Cooke, an astronomer at the Marshall Space Flight Center, the video sat on the computer for a week before Suggs analyzed it and found the 7.3-magnitude flash.

----------------------------------------------------------------
http://en.wikipedia.org/wiki/Giordano_B ... 8crater%29
<<Five monks from Canterbury reported to the abbey's chronicler, Gervase, that shortly after sunset on June 18, 1178, they saw two horns of light on the shaded part of the moon:

"This year, on the evening of June 18, when the moon, a slim crescent,
first became visible, a marvelous phenomenon was seen by several men
who were watching it. Suddenly the upper horn of the crescent was split
in two. From the midpoint of the division a flaming torch sprang up,
spewing out over a considerable distance fire, hot coals and sparks.
The body of the moon which was below writhed like a wounded snake.
This happened a dozen times or more, and when the moon returned to
normal, the whole crescent took on a blackish appearance."

The monks' observation took place during the Taurid meteor shower.

.............................................
http://antwrp.gsfc.nasa.gov/apod/ap051115.html
"Taurid meteor fireballs are likely pebble sized debris left by Comet Encke."
http://cometography.com/pcomets/002p.html
"Although the orbit of [Comet Encke] appears to have been stable for several thousand years, it is puzzling to astronomers that ancient or medieval comets have not been linked to comet Encke. It is especially perplexing considering the comet was seen with the naked eye during several returns during the 19th century."
.............................................

In 1976 the geologist Jack B. Hartung proposed that [the 1178 Canterbury report] described the formation of the Giordano Bruno crater. However, the question of Bruno's age is not that simple. The impact creating the 22 km wide crater would have kicked up enough debris to trigger a week-long, blizzard-like meteor storm on Earth -- yet no accounts of such a noteworthy storm of unprecedented intensity are found in any known historical records, including the European, Chinese, Arabic, Japanese and Korean astronomical archives.

An alternative theory holds that the monks just
happened to be in the right place at the right time
to see an exploding meteor coming at them
and aligned with the Moon.>>

by **Chris Peterson** » Thu Jan 31, 2008 5:37 am

Storm_norm wrote:I don't know of any recorded incident of a meteor hitting the moon. but how would you record it? its not like the meteor will light up like it does in the earth's atmosphere. the moon is probably pelted with dust all the time since it doesn't have an atmosphere like the earth's.

we can easily see meteor entering the earth's atmoshphere and follow the trail of the super heated material. that doesn't happen on the moon. how do you photograph dust hitting the moon?

There are dozens of images of meteoroids hitting the Moon, made over the last several years. Both amateurs and pros record videos of the shadowed part of the Moon during major meteor showers. There's no need for an atmosphere to see them; enough energy is liberated in the impact to show as a flash.

by **iamlucky13** » Wed Jan 30, 2008 11:30 pm

neufer wrote:(Tunguska sized) 15 (TNT) megaton March 1, 1954 Bikini "Bravo" test:

1500 (TNT) megaton TU24 asteroid if it had hit earth: ?????
http://apod.nasa.gov/apod/ap080130.html

For perspective, those dark spots near the expanding shockwave (this isn't the mushroom cloud...that comes later and is much bigger), are real-life, full-size battleships the navy parked there as part of the test.

By the way, play with numbers on the University of Arizona's impact effects calculator until you get a number of about 1.5 x 10^3 Megatons. It's not perfect, but they're model is pretty thorough for a description so tangible to the average visitor.

I entered:
250 m diameter
Dense Rock
23 km/s

The other parameters don't affect impact energy.

I dropped it in water, and from 100 km away, I felt a 5.7 earthquake, heard an 80dB boom, got pelted with 1/2" gravel, and probably got a sunburn from the fireball.

by **npsguy** » Wed Jan 30, 2008 9:35 pm

Arramon wrote:good ol' asteroids..

I'm just waiting for something to hit the moon... wake up the entire world about how little we can do concerning these objects that are everywhere in the solar system. Anyone know the last time something actually struck the moon and was recorded

Yep November 2005

http://www.astronomy.com/asy/default.aspx?c=a&id=3794

A meteoroid struck the Moon in early November, and NASA scientists caught the impact on tape.

NASA scientists at the Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Alabama, set up a telescope outside their office building to monitor flashes on the Moon's shadowed side.

Rob Suggs, team leader of NASA's space environments team, and Wesley Swift, a contractor who supports the environments team, connected an Astrovid StellaCam EX to an Orion 10-inch f/4.7 Newtonian on an Atlas mount as a 1-night project. The two were testing the feasibility of the monitoring technique. Video cable ran from the setup outside the engineering building to a desktop computer inside. According to Bill Cooke, an astronomer at the Marshall Space Flight Center, the video sat on the computer for a week before Suggs analyzed it and found the 7.3-magnitude flash.

by **Storm_norm** » Wed Jan 30, 2008 9:23 pm

I don't know of any recorded incident of a meteor hitting the moon. but how would you record it? its not like the meteor will light up like it does in the earth's atmosphere. the moon is probably pelted with dust all the time since it doesn't have an atmosphere like the earth's.

we can easily see meteor entering the earth's atmoshphere and follow the trail of the super heated material. that doesn't happen on the moon. how do you photograph dust hitting the moon?

how do you video something the size of a basketball or even a car hitting the moon? better yet if it was in the shadow of the moon.

there are rocks the size of a humans hand that hit the earth on pretty regular basis, I am not exactly sure how often it occurs, but it does happen. obviously we will never know exaclty how many have since 72% of the earth is covered in water and so most of the rocks are lost in the depths. Usually, the earth's atmosphere is good at vaporizing these rocks.

but the moon?? it has no defense and is probably pelted often.

oh and good luck photographing them

by **Arramon** » Wed Jan 30, 2008 8:32 pm

good ol' asteroids..

I'm just waiting for something to hit the moon... wake up the entire world about how little we can do concerning these objects that are everywhere in the solar system. Anyone know the last time something actually struck the moon and was recorded?

-=A=-

by **neufer** » Wed Jan 30, 2008 5:31 pm

William Roeder wrote:
neufer wrote:(Tunguska sized) 15 (TNT) megaton
There was a newspaper article today, 1/30/08, about new supercomputer models putting Tunguska at 3-5 megatons.

Yes, well I was just trying to be in the ball park as far as Tunguska was concerned.

The Tunguska event was probably equivalent to the 50 meter meteor that created "Barringer Crater" in Arizona (or the one currently heading towards Mars):
---------------------------------------------------
<<The object that excavated the "Barringer Crater" was a nickel-iron meteorite about 50 meters across. It is believed that about half of the impactor's 300,000 tonne (330,000 short tons) bulk was vaporized during its descent, before it hit the ground. The impact produced a massive explosion equivalent to at least 2.5 megatons of TNT. All life within a radius of three to four kilometers would have been killed immediately. The impact produced a fireball hot enough to cause severe flash burns at a range of up to 10 km (7 miles).>>
---------------------------------------------------
Generally a ton of impacting meteorite seems to produce the equivalent of ~20 tons of TNT explosion. Note that the 250 meter TU24 asteroid is 125 times the volume/mass of a 50 meter meteor and that it would suffer much less mass (& speed) loss going through Earth's atmosphere.
---------------------------------------------------
The main 1883 Krakatoa eruption is generally given as the
equivalent of 150 (TNT) megatons so it fits neatly between
the Bikini 15 MT H-bomb and the estimated 1500 MT TU24.
--------------------------------------
http://www.mystae.com/restricted/stream ... thera.html

<<"When Krakatoa exploded on August 26, 1883, it caused widespread destruction and loss of life on the coasts of Java and Sumatra. Blast waves cracked walls and broke windows up to 160 km. away. Tidal waves, reportedly up to 36 metres high, inundated the shores of the Sunda Strait, destroying nearly 300 towns and villages, and overnight more than 35,000 people lost their lives.">> - J. V. Luce, "The Changing Face of the Thera Problem"

<<"Krakatoa erupted noisily. It could be heard as much as 3,000 miles away on Rodrigues Island in the Indian Ocean. Vibrations shattered shop windows 80 miles off. The energy; released in the main explosion has been estimated to be equivalent to an explosion of 150 megatons of TNT. Ships navigating the seas in the vicinity of Krakatoa reported that floating pumice in some places had formed a layer about 3 m thick. Other shops, 160 miles off, reported that they were covered with dust three days after the end of the eruption. In fact the dust cloud completely shrouded the area, so that it was dark even 257 miles away from the epicenter. The period of darkness lasted twenty-four hours in places 130 miles distant and fifty-seven hours 50 miles away. The black-out in the immediate vicinity continued for three days and was so total that not even lamp-light could penetrate it.">> - Christos G. Doumas Thera - Pompeii of the Ancient Aegean, p. 141
--------------------------------------
The devastating earlier 1815 Tambora eruption with it's (year without a summer) global impact on weather was probably close to TU24 estimated 1500 (TNT) megatons although higher estimates have been given for Tambora.

[I just like to have a ballpark feel for such things.]

by **emc** » Wed Jan 30, 2008 5:30 pm

emc wrote:
Does an asteroid become a meteor or is an asteroid always an asteroid what about when it becomes tiny particles

Dr. Skeptic wrote:
Asteroid: in space
Meteor: in the atmosphere
Meteorite: on the ground or in your hand
Micro-Meteor or Micro- meteorite when less than .5 mm (sand or dust sized)

Should we come up with three more classifications for satellites???

by **emc** » Wed Jan 30, 2008 5:15 pm

http://www.cnn.com/2008/TECH/space/01/2 ... index.html

What has greater probability... asteroid crashes or satellite crashes

by **Dr. Skeptic** » Wed Jan 30, 2008 4:57 pm

William Roeder wrote:
neufer wrote:(Tunguska sized) 15 (TNT) megaton
There was a newspaper article today, 1/30/08, about new supercomputer models putting Tunguska at 3-5 megatons.

http://www.cnn.com/2008/TECH/space/01/2 ... index.html

by **npsguy** » Wed Jan 30, 2008 2:24 pm

That asteroid looks just like an old video games from the 1980's I used to play. Who knew that computer graphics were so ahead of their time?

by **Dr. Skeptic** » Wed Jan 30, 2008 1:48 pm

emc wrote:Does an asteroid become a meteor or is an asteroid always an asteroid what about when it becomes tiny particles

Asteroid: in space
Meteor: in the atmosphere
Meteorite: on the ground or in your hand
Micro-Meteor or Micro- meteorite when less than .5 mm (sand or dust sized)

Starship Asterisk*

Asteroid TU24 smoothed image. 1500 megaton (APOD 30 Jan2008)

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