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Bright Explosion on the Moon

science.nasa.gov

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Re: Bright Explosion on the Moon

#31

Post by InclinedPlane »

jlgreco wrote: post #16
InclinedPlane wrote: post #9

Earlier quoted context omitted.

Had that impact hit the ground it would have released over 100 kilotons of energy. It would have been far, far more destructive and deadly.

But without an atmosphere the shockwave from that 100 kiloton explosion should be pretty minimal (through the ground only), and any debris flung into the atmosphere would fall right back down on parabolic trajectories (or go into orbit), not linger in the sky for months/years. The danger posed by such an explosion, off the top of my head, would be getting hit by the object itself, getting hit by falling debris ejecte…

Sort of, there's still a blast wave from the vaporized rock, and there's still the ejecta blanket (which could easily ruin your day if any of it hit you).

Re: Bright Explosion on the Moon

#32

Post by japhyr »

pydanny wrote: post #6

Just wanted to say that I helped build this site. It's 2009/2010-era Django site built on feincms with a PostgreSQL backend. Originally it was a Plone site but after a year we realized it was too hard to meet the deadlines of NASA VIPs. So we moved it to Django. Also, myself and the other developers have NEVER been happy with the flash on the front page. :P

This doesn't strike me as bragging at all. I always appreciate the chance to connect people with projects.

I have learned from some of your posts about developing with Django, so I took a second look at the site after realizing you had helped build it.

Re: Bright Explosion on the Moon

#33

Post by [deleted] »

glurgh wrote: post #20
Zimahl wrote: post #4

Can someone explain to me why this would be bright? I understand that this should send up a fair amount of ejecta but wouldn't most of the light be just from a reflection of the sun off of the particles? If so, this isn't much of an explosion - it's just the most significant impact we've seen so far. I guess explosion is more interesting to the every-man.

Consider the absolutely insane energies involved - the report says "The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling 56,000 mph." That's a thing roughly half the size of a fridge. Traveling at a speed of about 25 kilometers, per second, coming to a full stop.

[deleted]

Re: Bright Explosion on the Moon

#34

Post by tnorthcutt »

pydanny wrote: post #6

Just wanted to say that I helped build this site. It's 2009/2010-era Django site built on feincms with a PostgreSQL backend. Originally it was a Plone site but after a year we realized it was too hard to meet the deadlines of NASA VIPs. So we moved it to Django. Also, myself and the other developers have NEVER been happy with the flash on the front page. :P

Why not replace the flash banner with an animated .gif?

Re: Bright Explosion on the Moon

#35

Post by saraid216 »

electronous wrote: post #28
alexmcroberts wrote: post #13

oh gawd, transformers has started...

oh gawd, reddit is leaking...

Aaaand obligatory,

> If your account is less than a year old, please don't submit comments saying that HN is turning into Reddit. (It's a common semi-noob illusion.)

http://ycombinator.com/newsguidelines.html

Re: Bright Explosion on the Moon

#36

Post by sigmavirus24 »

motoford wrote: post #18

I saw this once. It was quite a few years back, through my 8" dob in my front yard. I saw a flash and couldn't imagine what it could have been except an impact. After some research online that night I began to doubt myself, most people concluded it was too rare and would not be visible. The next day I saw someone asking in a newsgroup about the mysterious flash he had seen the night before while observing the moon th…

You know what you must do now. Pull that sucker out and start looking at the skies again, with your kids too if you have them.

Re: Bright Explosion on the Moon

#37

Post by lutorm »

rkaplan wrote: post #3

I found the footnote particularly interesting: "The Moon has no oxygen atmosphere, so how can something explode? Lunar meteors don't require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site…

Combustion doesn't make things explode; it just heats things up so they vaporize. But there are other ways to heat things up, too, and the end result is the same.

I thought it was a weird footnote. I mean, do people really think that the rock would burn even if there was oxygen?

Re: Bright Explosion on the Moon

#38

Post by lutorm »

dmckeon wrote: post #24
ghshephard wrote: post #8

Earlier quoted context omitted.

I wonder if the meteorite that exploded in the atmosphere over Russia did more or less damage than if it had struck the earth intact. Clearly Atmosphere makes a good shield for burning up the small meteorites - but I wonder if it exacerbates the damage from medium sized ones?

People tend to focus on the size of projectiles from space, but their great speed is often overlooked - from a simulator at: http://impact.ese.ic.ac.uk/ImpactEffects/ > Impact Velocity - This is the velocity of the projectile before it enters the atmosphere. The minimum impact velocity on Earth is 11 km/s. Typical impact velocities are 17 km/s for asteroids and 51 km/s for comets. The maximum Earth impact velocity fo…

The minimum impact velocity on Earth is 11km/s??? I beg to differ -- bodies can impact the Earth at arbitrarily low velocities. It depends on where they originate. There are clearly some assumptions being made there that aren't spelled out.

Re: Bright Explosion on the Moon

#39

Post by Retric »

lutorm wrote: post #37
rkaplan wrote: post #3

I found the footnote particularly interesting: "The Moon has no oxygen atmosphere, so how can something explode? Lunar meteors don't require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site…

Combustion doesn't make things explode; it just heats things up so they vaporize. But there are other ways to heat things up, too, and the end result is the same. I thought it was a weird footnote. I mean, do people really think that the rock would burn even if there was oxygen?

I suspect many meteors can and will combust. Lot's of things love oxygen bonds once they get enough energy and there is not a lot oxygen or heat in space.

PS: Think Class D Fire http://en.wikipedia.org/wiki/Fire_classes

Re: Bright Explosion on the Moon

#40

Post by acdha »

pydanny wrote: post #6

Just wanted to say that I helped build this site. It's 2009/2010-era Django site built on feincms with a PostgreSQL backend. Originally it was a Plone site but after a year we realized it was too hard to meet the deadlines of NASA VIPs. So we moved it to Django. Also, myself and the other developers have NEVER been happy with the flash on the front page. :P

I would be remiss in not thanking the Varnish cache developers, too: it's using CloudFront now but Varnish came in quite handy when we suddenly jumped from mostly images to some large videos like http://science.nasa.gov/science-news/science-at-nasa/2010/21... shortly after launch.

The scariest bit of code was probably the scraper + html5lib normalizer I used to migrate something like 15 years of legacy static HTML content from two separate into the CMS using a large pile of selectors and cleanup heuristics.

http://chris.improbable.org/2009/10/16/deploying-django-site... describes how the site was packaged using RPM so we could fit within the more traditional IT model used by the production sysadmins.

One open-source tool which came out of this was https://github.com/shentonfreude/webcompare which we used to bulk-compare the old and new sites to confirm that all of our legacy URLs either redirected or were intentionally 404/410ed.

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