Space Debris Rains Down on Earth
Low Earth Orbit is the region of space within 1,200 miles of the Earth's surface. It is the most concentrated area for orbital debris. Photo by NASA Orbital Debris Program Office.
On a January night in 1997, Lottie Williams of Tulsa, Okla. was strolling through the park with friends when she saw a flash of light stream across the sky. And then, bam!, a shard of metal the size of a soda can from a disintegrating Delta 2 booster rocket nailed her on the shoulder. She is the only person known to have ever been struck by falling space debris. Since the object wasn't heavy, it startled, but didn't harm her.
But it's a little known fact that approximately once a week, a large object like a defunct spacecraft or a rocket body falls out of space and plunges back to Earth, likely landing in the ocean, or a vast area like Siberia or the Canadian outback. And smaller objects are falling from space back to Earth daily in a fiery descent. The Antares rocket for example, which launched on April 21, crashed back to Earth on Saturday.
"About once a year, we'll find piece of spacecraft or a rocket body that survived reentry," said Nicholas Johnson, NASA's chief scientist for orbital debris.
While this cascade of raining space junk sounds menacing, the objects actually pose little risk to humans. Smaller objects usually burn up during reentry and no one object, Johnson said, poses a larger than 1 in 10,000 risk to humans.
The Department of Defense has a space surveillance network that tracks tens of thousands of man-made objects in orbit, including the biggest baddest pieces of space junk out there. These are the 23,000 objects bigger than a baseball, or 10 cm or larger in size. And scientists also monitor the objects reentering the Earth's atmosphere.
"We track, on average, two to three objects reentering the Earth's atmosphere each day," said Defense department spokesperson Lt. Col. Monica Matoush.
Flying through space at about 7 miles per second, these objects can wreak havoc on a spacecraft or satellite. And they're potentially harmful to an astronaut doing a spacewalk. The defense department sends out warnings of large objects in the trajectory of a spacecraft or satellite about three days in advance.
Then there are the smaller ones - the half million 1 cm objects and the 100 million 1 mm objects.
"Small objects can do a lot of damage to a spacecraft if it's not adequately protected," Johnson said. "But the shielding is such that we can defend against objects up to 1 cm."
Critical components of the International Space Station, for example, are shielded to withstand debris up to 1 cm. Once or twice a year, Johnson said, NASA will maneuver the entire 400-metric ton space station to avoid massive space junk barreling toward it. They also perform so-called "collision avoidance maneuvers" with the 1,100 operational robotic spacecraft in low-Earth orbit.
With these shields protecting against smaller objects and the defense department monitoring the larger ones, it's the in-between pieces -- the 5 cm objects -- which pose the greatest threat, Johnson said.
On February 10, 2009, the Iridium 33 satellite collided with the defunct Kosmos 2251 satellite at a speed of 26,000 miles per hour, creating 2,000 additional pieces of space debris. And in 1996, a piece of space debris collided with the Cerise satellite, tearing off a portion of the satellite's gravity-gradient stabilization boom, damaging the spacecraft.
"If a 5 cm piece of debris were to hit any spacecraft, it could cause very severe damage and loss of the mission," Johnson said.
From NPR: The European Union is banning three popular pesticides, in hope of restoring populations of honeybees
Cicadas clean themselves using... dew drops?
President Obama tells this epic Civil War joke at the National Academy of Sciences 150th anniversary celebration. Buzzfeed has the video.
From the Howard Hughes Medical Institute: Why so many adults have lost the ability to digest milk.
This is Discover Magazine's third post in a series on a simulated Mars mission. Five scientists and engineers are isolated on a Hawaiian volcano, sent by NASA to study how food for astronauts may be improved. Turns out faced with unappetizing dried meals, astronauts eat less, and lose weight, posing stamina and performance problems. Find the first post here.
Congress is debating major changes to the $7 billion a year that the National Science Foundation spends on basic research.
From New Scientist: "Mind reading can be as simple as slapping a sticker on your forehead. An "electronic tattoo" containing flexible electronic circuits can now record some complex brain activity as accurately as an EEG. The tattoo could also provide a cheap way to monitor a developing fetus."
Rebecca Jacobson, Tom Kennedy and David Pelcyger contributed to this post.