http://www.ovelho.com/link.php?link=http://www.spaceref.com/news/viewsr.html?pid=14887

Near-Earth Asteroid 2004 MN4 Reaches Highest Score To Date On Hazard Scale

Don Yeomans, Steve Chesley and Paul Chodas
NASA's Near Earth Object Program Office


A recently rediscovered 400-meter Near-Earth Asteroid (NEA) is predicted to pass near the Earth on 13 April 2029. The flyby distance is uncertain and an Earth impact cannot yet be ruled out. The odds of impact, presently around 1 in 300, are unusual enough to merit special monitoring by astronomers, but should not be of public concern. These odds are likely to change on a day-to-day basis as new data are received. In all likelihood, the possibility of impact will eventually be eliminated as the asteroid continues to be tracked by astronomers around the world.

December 24 Update: 2004 MN4 is now being tracked very carefully by many astronomers around the world, and we continue to update our risk analysis for this object. Today's impact monitoring results indicate that the impact probability for April 13, 2029 has risen to about 1.6%, which for an object of this size corresponds to a rating of 4 on the ten-point Torino Scale. Nevertheless, the odds against impact are still high, about 60 to 1, meaning that there is a better than 98% chance that new data in the coming days, weeks, and months will rule out any possibility of impact in 2029.



The orbit of 2004 MN4 about the Sun is shown in blue. Much of the asteroid's orbit lies within the Earth's orbit, which is the outermost white circle. The positions of the asteroid and the Earth are shown for December 23, 2004, when the object was about 14 million km (9 million miles) away from the Earth.

This object is the first to reach a level 2 (out of 10) on the Torino Scale. According to the Torino Scale, a rating of 2 indicates "a discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. While meriting attention by astronomers, there is no cause for public attention or public concern as an actual collision is very unlikely. New telescopic observations very likely will lead to re-assignment to Level 0 [no hazard]." This asteroid should be easily observable throughout the coming months.

The brightness of 2004 MN4 suggests that its diameter is roughly 400 meters (1300 feet) and our current, but very uncertain, best estimate of the flyby distance in 2029 is about twice the distance of the moon, or about 780,000 km (480,000 miles). On average, an asteroid of this size would be expected to pass within 2 lunar distances of Earth every 5 years or so.

Most of this object's orbit lies within the Earth's orbit, and it approaches the sun almost as close as the orbit of Venus. 2004 MN4's orbital period about the sun is 323 days, placing it within the Aten class of NEAs, which have an orbital period less than one year. It has a low inclination with respect to the Earth's orbit and the asteroid crosses near the Earth's orbit twice on each of its passages about the sun.



The cloud of possible positions of asteroid 2004 MN4 relative to Earth on April 13, 2029 is shown in white. The Moon's orbit is also shown, for scale. The blue arrow indicates the direction of motion of the cloud as it sweeps past the Earth. A tiny portion of the cloud intersects the Earth. A slight dip in the cloud due to the Earth's gravity is clearly evident. The length of the cloud is directly related to current uncertainties in our knowledge of this new object's orbit. As astronomers track this asteroid over the coming weeks and months, the orbit will become better determined and the cloud will shorten, converging on a true position which, in all likelihood, will be well removed from the Earth.

2004 MN4 was discovered on 19 June 2004 by Roy Tucker, David Tholen and Fabrizio Bernardi of the NASA-funded University of Hawaii Asteroid Survey (UHAS), from Kitt Peak, Arizona, and observed over two nights. On 18 December, the object was rediscovered from Australia by Gordon Garradd of the Siding Spring Survey, another NASA-funded NEA survey. Further observations from around the globe over the next several days allowed the Minor Planet Center to confirm the connection to the June discovery, at which point the possibility of impact in 2029 was realized by the automatic SENTRY system of NASA's Near-Earth Object Program Office. NEODyS, a similar automatic system at the University of Pisa and the University of Valladolid, Spain also detected the impact possibility and provided similar predictions.



Animation showing the cloud of possible positions of asteroid 2004 MN4 relative to Earth in April 2029 is shown in white. The Moon's orbit is also shown, for scale. A tiny portion of the cloud intersects the Earth. The length of the cloud is directly related to current uncertainties in our knowledge of this new object's orbit. This animation will repeat itself ten times.

This has been generating considerable buzz amongst "minor planet" astronomers over the last few days. It is bright enough to be seen by a good amateur telescope setup but much too dim for binoculars or naked eye (mag 19.4).

The position & projected path should be nailed down pretty quick, days to a couple of weeks. Everything else - size, rotation, mass - will be tricky. Some amateurs are working very hard on the rotation problem but no reliable results yet, and radar time isn't scheduled until late January.

My favorite quote from an astronomer at the Space Science Institute, trying to keep the chance of impact issues in perspective:

Quote:

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My projected age in 2029 is 85, so this is only a minor perturbation in my chance of death by then. So I view all this with, you could say, detached interest.

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http://neo.jpl.nasa.gov/news/news148.html

Someone made a precovery and no impact in 2029. A precovery is finding an object in an older picture taken some time ago - that gives you a longer timeline to work with. It's common for important objects like this to involve searches on plates going back 50+ years.

In any case this one was moving slowly as such things go and wouldn't have been wipe-out-humans-and-start-over (unfortunately). An ocean strike might have been no worse than the tsunami yesterday.

Possibility of an Earth Impact in 2029 Ruled Out for Asteroid 2004 MN4
Don Yeomans, Steve Chesley and Paul Chodas
NASA's Near Earth Object Program Office
December 27, 2004

Over the past week, several independent efforts were made to search for pre-discovery observations of 2004 MN4. These efforts proved successful today when Jeff Larsen and Anne Descour of the Spacewatch Observatory near Tucson, Arizona, were able to detect and measure very faint images of asteroid 2004 MN4 on archival images dating to 15 March 2004. These observations extended the observed time interval for this asteroid by three months allowing an improvement in its orbit so that an Earth impact on 13 April 2029 can now be ruled out.

As is often the case, the possibility of future Earth impacts for some near-Earth objects cannot be entirely ruled out until the uncertainties associated with their trajectories are reduced as a result of either future position observations, or in this case, heretofore unrecognized, pre-discovery observations. When these additional observations were used to update the orbit of 2004 MN4, the uncertainties associated with this object's future positions in space were reduced to such an extent that none of the object's possible trajectories can impact the Earth (or Moon) in 2029.

In the accompanying diagram, the most likely position of asteroid 2004 MN4 is shown at the end of the blue line near the Earth on 13 April 2029. However, since the asteroid's position in space is not perfectly known at that time, the white dots at right angles to the blue line are possible alternate positions of the asteroid. Neither the nominal position of the asteroid, nor any of its possible alternative positions, touches the Earth, indicating that an Earth impact in 2029 is ruled out.

Updated Set of Possible Positions of 2004 MN4 on April 13, 2029


The passage of the asteroid by the Earth in 2029 alters its subsequent trajectory and expands the asteroid's position uncertainty region (i.e., the line of white dots increases in extent) so the asteroid's subsequent motion is less certain than it was prior to the 2029 close Earth approach. However, our current risk analysis for 2004 MN4 indicates that no subsequent Earth encounters in the 21st century are of any concern.

Bullshit. We´re all gonna die.

I'll take the same odds as winning the Powerball. Not that I was planning on being here in 2029 anyway.

What a depressing thought.

Beam me up, Scotty, before 2029

Now they´ll have the recalculate all this jingamaboob, cause the Asian tsunami was strong enough to change, albeit very slighty, the axis of Earth.

Day the Earth was shaken to its core
Science writer Leigh Dayton
December 29, 2004

WHEN it hit, the earthquake that unleashed Sunday's killer waves caused the Earth to wobble on its axis and changed the regional map forever.

According to experts, the 9.0-magnitude earthquake that hit 250km southeast of Sumatra was so powerful that some of the smaller islands off the southwest coast of the island may have shifted southwest by 20m.

"That is a lot of slip," said geophysicist Ken Hudnut of the US Geological Survey.

Further, Dr Hudnut claimed that the northwestern tip of Sumatra might also have moved southwest - possibly as much as 36m - when the Indian Plate dived beneath the Burma plate, causing earth-shattering uplift and triggering the tsunami. Geoscience Australia seismologist Cvetan Sinadinovski said the exact displacement remained to be confirmed by measurements made by global positioning satellites.

Dr Sinadinovski was sceptical of Dr Hudnut's claim that the event rocked the Earth off its axis, claiming instead that it was more a "glitch" in planetary rotation.

Still, Dr Sinadinovski agreed that the quake had made the Earth vibrate.

"It made the Earth ring like a bell," he said.

Dr Sinadinovski added that the Sumatra quake was worsened by an 8.1-magnitude earthquake that had struck on Christmas eve, about 800km southeast of Hobart, near Macquarie Island and the underwater "Macquarie Rise".

"That earthquake was not a direct trigger to the Sumatran event, but it had the potential to speed up the release of energy; it was released more quickly," he explained.

The fact that a major earthquake occurred just three days before the one on Sunday has raised scientific speculation that major shakes may come in clusters, either on a global basis or along fault lines.

In Pasadena, California, geologist Kerry Sieh noted that clumps of quakes hit Turkey in the 1930s and 40s and whoppers slammed Alaska in the 50s and 60s.

"There were other periods of time when there were global flurries of earthquakes," he said, noting that five of the 10 largest earthquakes of the 20th century had hit between 1957 and 1965.

Two more struck in 1950 and 1952. Earth was quake-free from 1989 to 1994, then it was rocked by four in the next two years, said Professor Sieh.

The biggest known earthquake, was a 9.5-magnitude event that hit Chile in May 1960.

The next largest was the 9.2-magnitude event that hit in Alaska's Prince William Sound in March 1964.

Despite historical clusters - and 31 aftershocks since Sunday of between 5.5 and 7.3 magnitude - it's impossible to know if Sunday's plate-buster will spawn more major quakes, Dr Sinadinovski said.

"We can expect large earthquakes to continue occurring in these zones, but the exact timing is nearly impossible to predict," he concluded.

Tsunami reshapes map of Asia

AFP[ WEDNESDAY, DECEMBER 29, 2004 12:00:12 AM]

LOS ANGELES: The earthquake that unleashed deadly tidal waves on Asia was so powerful that it made the Earth wobble on its axis and permanently altered the regional map, US geophysicists have said.

The 9-magnitude temblor that struck 250 km southeast of Sumatra Island on Sunday may have moved small islands as much as 20 metres, according to one expert.

“That earthquake has changed the map,” US geological survey (USGS) expert Ken Hudnut said. “Based on seismic modelling, some of the smaller islands off the southwest coast of Sumatra may have moved further southwest by about 20 metres. That is a lot of slip.”

The northwestern tip of the Indonesian territory of Sumatra may also have shifted to the southwest by around 36 metres, Mr Hudnut said.

In addition, the energy released as the two sides of the undersea fault slipped against each other made the Earth wobble on its axis, Mr Hudnut said.

“We can detect very slight motions of the Earth and I would expect that the Earth wobbled in its orbit when the earthquake occurred due the massive amount of energy exerted and the sudden shift in mass,” Mr Hudnut said.

However, Stuart Sipkin, of the USGS National Earthquake Information Centre in Golden Colorado, said it was more likely that the islands off Sumatra had risen higher out of the sea than they had moved laterally.

“In this case, the Indian plate dived below the Burma plate, causing uplift, so most of the motion to the islands would have been vertical, not horizontal,” Mr Sipkin said.

OK, the guy predicting the "wobble" (nutation) is predicting something on the order of 1 part in 30,000,000,000. So it'a not as absurd to make the claim as it seems, although measuring the affect (and not measuring something else instead) seems tough.

We'll see if anyone is brave enough to submit a paper for peer review.