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from the making-humans-not-be-like-the-dinosaurs dept.
EurekAlert reports: "NASA to map the surface of an asteroid"
NASA's OSIRIS-REx spacecraft will launch September 2016 and travel to a near-Earth asteroid known as Bennu to harvest a sample of surface material and return it to Earth for study. The science team will be looking for something special. Ideally, the sample will come from a region in which the building blocks of life may be found.
The Daily Mail points out:
Bennu crosses Earth's orbit once every six years and is set to pass between the moon and our planet in 2135.
Scientists are worried the 500-metre wide asteroid's orbit could be tweaked by Earth's gravity as it passes by, causing it to smash into our planet later in the century.[...] 'We estimate the chance of impact at about one in 2,700 between 2175 and 2196,' [Prof. Lauretta] said.
It seems this (paywalled) Sunday Times article might be the original source for the quotes from Prof. Lauretta. Here are some excerpts from the article:
"Bennu is a carbonaceous asteroid, an ancient relic from the early solar system that is filled with organic molecules," said Lauretta.
"Asteroids like Bennu may have seeded the early Earth with this material, contributing to the primordial soup from which life emerged."
[...] For scientists, the chance of obtaining chunks of a carbonaceous asteroid is exciting. For the rest of us, however, Osiris-Rex's most important task may be the measurements it makes of a bizarre and newly discovered force that can send asteroids careering around the solar system and potentially towards Earth.
"The Yarkovsky effect is the force that acts on an asteroid when it absorbs sunlight and then radiates it back into space as heat. It acts like a small thruster, constantly changing its course," said Lauretta. "Bennu's position has shifted 160km [100 miles] since 1999."
It is these forces that make Bennu's trajectory so hard to predict after 2135's near-miss. It is expected to pass Earth at a distance of about 180,000 miles, well inside the moon's orbit and close enough to alter the asteroid's path so it may hit our planet on a future orbit.
(Score: 3, Interesting) by VLM on Monday August 01 2016, @01:04PM
"The Yarkovsky effect is the force that acts on an asteroid when it absorbs sunlight and then radiates it back into space as heat. It acts like a small thruster, constantly changing its course," said Lauretta. "Bennu's position has shifted 160km [100 miles] since 1999."
Maybe if its on a collision course global warming could save us.
I'm too lazy to run the numbers but "obviously" there is a small net force due to the sunlit side of the planet being warmer and radiating away more IR than the cold dark side of the earth. Surely that force varies with global warming due to changes in dew point and fuzzy math and butterflies flapping wings causing chaos and stuff. I'd be shocked if the net force were exactly zero WRT delta in average surface temp.
Any force will have an effect on orbital position that cascades over time. Space is really freaking big and the earth is really freaking small like 4000 miles diameter. So if an asteroid were bullseye to hit the earth in 50Myrs killing everything again dinosaur style, it turns out that moving the earth (or anything) 5000 miles in 50Myrs is 5000 / 50e6 / 365 / 24 or about ten billionths of a mile per hour. To one sig fig, not accounting for leap years doesn't matter a hell of a lot. Also the relevant atmosphere is a lot thinner than 1000 miles, in fact 100 miles up is more than adequate for a miss. But whatever.
I have no idea how ten billionths of a MPH fits in with the surface of the earth as an infrared thruster. Note that there's many orders of magnitude to play with if you want.
I'm forever coming up with interesting hard sci fi novel ideas and this could make an interesting plot. Space aliens use propaganda in the 1900s to convince us to burn all our planets oil in 100 years to make sure a planet killer asteroid misses us in 50M years. Or the reverse, I suppose, burning the oil today is moving us into the crosshairs in 50 Myrs. Either way it would make a semi-entertaining hard sci fi novel plot. In my infinite spare time. Or James Bond villain time they just want to make sure the "right" country is hit by a small meteor, big enough to be entertaining.
(Score: 2) by FatPhil on Monday August 01 2016, @03:55PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by VLM on Monday August 01 2016, @04:48PM
Agreed it would be more efficient from an engineering standpoint to launch a mission to the asteroid with a truly huge can of paint. Which as a tangent would be an interesting hard sci fi plot.
Hmm so the helpful space aliens need to alter the orbit without a mission because 1) we might fail to launch a mission but its hard to screw up "set stuff on fire" and 2) They are not here or not here with high tech, like the usual stranded astronaut story or some kind of radio communication. or 3) alternatively they just like messing with us. Space aliens get bored too.