March 1, 2011
What’s Hitting Earth?
By Dauna Coulter, Science @ NASA
Every day about 100 tons of meteoroids -- fragments of dust and gravel and sometimes even big rocks "“ enter the Earth's atmosphere. Stand out under the stars for more than a half an hour on a clear night and you'll likely see a few of the meteors produced by the onslaught. But where does all this stuff come from? Surprisingly, the answer is not well known.
Now NASA is deploying a network of smart cameras across the United States to answer the question, What's Hitting Earth?
Did that meteor you saw blazing through the sky last night come from the asteroid belt? Was it created in a comet's death throes? Or was it a piece of space junk meeting a fiery demise?
"When I get to work each morning and power up my computer, there's an email waiting with answers," says William Cooke, head of NASA's Meteoroid Environment Office. "And I don't have to lift a finger, except to click my mouse button."
Groups of smart cameras in the new meteor network triangulate the fireballs' paths, and special software1 uses the data to compute their orbits and email Cooke his morning message.
"If someone calls me and asks 'What was that?' I'll be able to tell them. We'll have a record of every big meteoroid that enters the atmosphere over the certain parts of the U.S. Nothing will burn up in those skies without me knowing about it!"
In other U.S. meteor networks, someone has to manually look at all the cameras' data and calculate the orbits "“ a painstaking process.
"With our network, our computers do it for us "“ and fast," says Cooke.
The network's first three cameras, each about the size of a gumball machine, are already up and running. Cooke's team will soon have 15 cameras deployed east of the Mississippi River, with plans to expand nationwide2. Cooke is actively seeking schools, science centers, and planetaria willing to host his cameras. Criteria are listed in the notes at the end of this story.
In addition to tracking fireballs and their orbits, Cooke's system gives him other valuable information.
"It provides data on meteor speed as a function of size "“ and this is critical to calibrating the models we use in designing spacecraft."
Meteorite hunters will reap benefits too. By determining a bright fireball's trajectory through the atmosphere, the network's software can calculate whether it will plunge to Earth and pinpoint the impact location fairly precisely.
"And when we collect the meteorite chunks, we'll know their source. I could be holding a piece of Vesta in my hand.3 It would be like a free sample return mission!"
Opportunities like that, however, will be rare. "Most meteorites fall in the ocean, lakes, forests, farmer's fields, or the Antarctic," says Rhiannon Blaauw, who assists Cooke. "And the majority of those meteorites will never be found. But our system will help us track down more of them."
All cameras in the network send their fireball information to Cooke and to a public website, fireballs.ndc.nasa.gov. Teachers can contact Cooke at [email protected] to request teacher workshop slides containing suggestions for classroom use of the data. Students can learn to plot fireball orbits and speeds, where the objects hit the ground, how high in the atmosphere the fireballs burn up, etc.
Cooke gives this advice to students and others who want to try meteor watching on their own:
"Go out on a clear night, lie flat on your back, and look straight up. It will take 30 to 40 minutes for your eyes to become light adapted, so be patient. By looking straight up, you may catch meteor streaks with your peripheral vision too. You don't need any special equipment -- just your eyes."
One more thing -- don't forget to check the website to find out what you saw!
(1) The smart meteor network uses ASGARD (All Sky and Guided Automatic Realtime Detection) software, developed at the University of Western Ontario with both NASA and Canadian funding, to process the information and perform the triangulation needed to determine the orbits and origins of the fireballs. The Southern Ontario Meteor Network, or SOMN, composed of seven cameras, also uses the ASGARD system.
(2) The cameras will be deployed in clusters of 5. One group will be spread over the Southeast US, another in the Ohio and Kentucky area (to overlap with the Southern Ontario Meteor Network, or SOMN), and another along the Atlantic coast in the NorthEast. "Our hope is that at least one of the three regions will have clear skies at any given time."
Here are the criteria that must be met for a location to be considered as a camera site:
1. Location east of the Mississippi River
2. Clear horizon (few trees)
3. Few bright lights (none close to camera)
4. Fast internet connection
(3) The meteorite will have been altered by its journey, so it is not a pristine sample, but, says Cooke, it is a good enough sample to give you basic characteristics of the non-volatiles.
Image 1: A Southern Delta Aquarid fireball streaks over one of the network cameras in July 2010: movie.
Image 2: The orbit of the Southern Delta Aquarid meteor (red) was a good match to that of the parent comet (blue).