The 36th Carnival of Space is up at Steinn Sigurðsson’s Dynamics of Cats site. Standing out this week are the items flowing in from the American Astronomical Society meeting in Austin, which ran until Friday. The best place to get the overview is Universe Today, but both Random thoughts of an astro major and Bad Astronomy have tracked events closely. Also noteworthy this time around is the news that the asteroid strike on Mars is now effectively ruled out, the odds falling to one in 10,000.
Image: 2007 WD5 from the University of Hawaii 2.2-meter telescope on Mauna Kea, Hawaii. The circled dot is the asteroid (click to enlarge; it’s at dead center, in a green circle). Other dots are artifacts from cosmic rays. The stars are trailed because the telescope is tracking the asteroid as it moves among the stars. Credit: Tholen, Bernardi, Micheli with support from the National Science Foundation.
Too bad, as the opportunities for close observation of such a hit would have taught us much about planetary impacts, and perhaps provided a wake-up call to the budget cutting at Arecibo’s planetary radar. How these things are calculated is interesting in itself, and the Near Earth Object Program site explains how the numbers can seem to vary so wildly:
The sequence of updates over the last few weeks has been typical of past potential impact scenarios, with the odds of impact initially surging and later plummeting towards zero. Early on, the uncertainty region is very large and the probability of impact is rather low. As the uncertainty narrows, but still includes the planet, the probability initially increases. But eventually, as in this case, the uncertainty region shrinks to the point that it no longer overlaps the planet, and the probability of impact begins a precipitous decline. This rise and fall of the computed hazard was most notably seen in Dec. 2004 when asteroid 99942 Apophis briefly reached a 2.7% chance of impact with Earth in April 2029. In every case, the height and the timing of the peak probability – and the subsequent decline – cannot be known until the uncertainty region has shrunk to the point where it no longer intersects the planet.
All of which is useful to keep in mind as we continue to scan the skies for Earth-crossing asteroids. NASA’s Spaceguard Survey is aimed at finding 90 percent of such objects larger than one kilometer in size, a goal that the Near Earth Object Program site says will be met within several years. 2007 WD5 is now said to pose no threat to either Mars or the Earth for the next century. The best estimate is that it will pass 26,000 kilometers from the Martian planetary center on January 30, and almost certainly no closer than 4000 kilometers from the surface (thanks to Hans Bausewein for a correction on the distance).
“It should pass 26,000 kilometers from the Martian planetary center on January 30, some 4000 kilometers from the surface.”
That means Mars’ diameter would be 44000 km
If I remember the original article stated something like: ” at least 4000 kilometers from the surface”
Exactly so, Hans, and so corrected in the text, with your help. Thanks!
Did you heard the news ?
http://www.lpl.arizona.edu/~rory/prediction/
The First Successful Prediction of an Exoplanet
Did the author do any study on Alpha Centauri, or can his method be used in AC case ?
Xyz, it’s an interesting story indeed, and in queue for an article and discussion here early next week. I’ll have more details about it then, once I’ve had the chance to study the exoplanet prediction paper. More to come!
I think its too bad it will miss Mars. Here was a big opportunity for scaring the pants off earthlings so they take a bollide collision with earth as seriously as we take global warming.
Its sad if we got wiped out over a known threat, which we could have prepared for but there was neither will nor funding.
That would make us possibly the stupidest intelligent species in the cosmos. And even more silly if we are truly alone in the Universe.
Phobos is 9,378 kilometers distant from Mars and Deimos is at 23,459 kilometers, so, let me ask, have the calculations for the asteroid impact included figuring out if it could either of these two bodies?
What a story that would be if big ol’ fat Mars is missed but teeny tiny Deimos is hit, eh?
Phobos is so small that gravity isn’t large enough to mold the moon into a sphere. Rather, it is shaped more like a potato about 26 kilometers long by about 22 kilometers across. Deimos, the smaller of the two, is only about 15 kilometers long by 12 kilometers across.
So, if hit just right smack in the “thinnest part,” could there be enough energy to break, say, Deimos, into pieces?
I remember a wonderful essay by Issac Asimov about these two. Called them diamonds in the sky, cuz they’d twinkle bigtime with their tumbling odd shapes reflecting light a lot/little. Then he asked the question: “Are they space ships hanging out there to watch us on Earth?” He thought they were too small to have been made by the planet forming dynamics and had to be either captured passers-by or, hey, why not hollowed-out ships?
Gotta love the mysteries.
Edg
Edg, the old hollow moon theory is long gone, but it was fun, and I remember speculations about that (didn’t know about the Asimov essay, but would still enjoy reading it). And yes, wouldn’t that be quite an event if we lined up a true celestial bullseye between the incoming asteroid and one of these moons?
Asteroid 2007 WD5 will not impact Mars on January 30!
Authors: Malgorzata Krolikowska, Grzegorz Sitarski
(Submitted on 11 Jan 2008)
Abstract: The Monte Carlo method of the nominal orbit clonning was applied to the case of 2007 WD5, the asteroid from the Apollo group. Calculations based on 33 observations from the time interval of 2007 11 08 – 2008 01 02 showed that the asteroid will pass near planet Mars at the minimum distance of 10.9\pm 2.9 R_{Mars}, what implies that probability that 2007 WD5 strike the planet decreased to the value of 0.03% from the value of about 3–4% previously announced by NASA. The additional observations taken on January 3–9 reduce further the asteroid’s impact chances, effectively to nil: the asteroid will pass near planet Mars at the minimum distance of 8.4\pm 1.1 R_{Mars}.
Comments: 7 pages
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0801.1771v1 [astro-ph]
Submission history
From: Malgorzata Krolikowska [view email]
[v1] Fri, 11 Jan 2008 12:46:45 GMT (189kb,D)
http://arxiv.org/abs/0801.1771
Space rock misses Mars today:
http://www.space.com/scienceastronomy/080130-mars-miss.html
Assuming it did miss, how soon will it close enough to Earth
again for astronomers to detect it? And has anyone calculated
when or if it might hit Mars or even Earth in the future?
Mars study shows oceans of water bubbled up from below
NASA image revealing formations consistent with water
outbursts carving channels and laying terraced deposits.
by Staff Writers
Paris (AFP) Feb 20, 2008
Fan-shaped deltas at the edge of huge basins scattered
across Mars were probably formed by a titanic influx of
water, gushing from the bowels of the Red Planet,
according to study released Wednesday.
The origin and morphology of the deltas, studded with
curious step-like terraces, have perplexed scientists since
they were first observed three years ago.
Today the surface of Mars is bone dry, but a growing
body of evidence suggests as much as a third of its
surface was at one time covered with oceans.
But scientists have differed — sometimes sharply — as
to exactly where the water came from.
A quartet of researchers at Utrecht University in the
Netherlands led by Erin Kraal, using satellite images
and topographical data from the Mars Orbiter,
hypothesised that these unique formations could only
have originated from a single, massive basin-filling event.
Their study, published in Nature, also concluded that the
water rushed in over a period measured in tens of years,
not millions, as many scientists had thought.
And not just a little bit, either.
Full article here:
http://www.marsdaily.com/reports/Mars_study_shows_oceans_of_water_bubbled_up_from_below_999.html