Apophis and the KeyholeApophis and the Keyhole

SOLAR SYSTEM

• sun

• planets, dwarf planets, and moons

• asteroids and comets

• dust

• lots of space between everything

Bob Perry:http://www.cfa.harvard.edu/iau/lists/InnerPlot.html

The orbits of the major planets are shown in light blue: the current location of the major planets is indicated by large colored dots. The locations of the minor planets, including numbered and multiple-apparition/long-arc unnumbered objects, are indicated by green circles. Objects with perihelia within 1.3 AU are shown by red circles. Objects observed at more than one opposition are indicated by filled circles, objects seen at only one opposition are indicated by outline circles. The two "clouds" of objects 60° ahead and behind Jupiter (and at or near Jupiter's distance from the sun) are the Jupiter Trojans, here colored deep blue. Numbered periodic comets are shown as filled light-blue squares. Other comets are shown as unfilled light-blue squares.

In this view, objects in direct orbits (most of the objects in this plot) move counterclockwise and the vernal equinox is towards the right. (The equinox directions are the direction of the sun

as seen from the earth.) The plot is correct for the date given at the bottom of the plot.

Bob Perry:http://www.cfa.harvard.edu/iau/lists/InnerPlot.html

The orbits of the major planets are shown in light blue: the current location of the major planets is indicated by large colored dots. The locations of the minor planets, including numbered and multiple-apparition/long-arc unnumbered objects, are indicated by green circles. Objects with perihelia within 1.3 AU are shown by red circles. Objects observed at more than one opposition are indicated by filled circles, objects seen at only one opposition are indicated by outline circles. The two "clouds" of objects 60° ahead and behind Jupiter (and at or near Jupiter's distance from the sun) are the Jupiter Trojans, here colored deep blue. Numbered periodic comets are shown as filled light-blue squares. Other comets are shown as unfilled light-blue squares.

In this view, objects in direct orbits (most of the objects in this plot) move counterclockwise and the vernal equinox is towards the right. (The equinox directions are the direction of the sun

as seen from the earth.) The plot is correct for the date given at the bottom of the plot.

http://neo.jpl.nasa.gov/orbits/ ==> select Apophis

• Apophis is about three times the size of the asteroid thatmade Meteor Crater in Arizona 50,000 years ago

• It has a close encounter with the Earth every seven years

• In 2029 it will flyby closer than the orbits of synchronous satellites

• There is a large uncertainty in its exact position in that flyby

• If it passes through a 610 meter "keyhole” in that uncertainty, it will hit the Earth in 2036

mathematical model

. . . changes in the 17th significant digit, roundedand truncated by typical computing systems, make the difference between an Apophis hit or a miss by one Earth radius. That is, even computational noisein the hardware doing the calculation, never mindthe measurement and physical error sources thatwill always exist, is an issue.

Jon Giorgini CCNet #40/07 - 21 February 2007

asteroid

1997 XF11

early model

2028 flyby

~18 month “year”

asteroid

1997 XF11

model with

“precovery”

data

2028 flyby

Horizontal gradient map of the Bouguer gravity anomaly over the Chicxulub crater (North is up.). The coastline is shown as a white line. A striking series of concentric features reveals the location of the crater. This image was constructed from gravity measurements taken by Petróleos Méxicanos beginning in 1948 in the course of petroleum exploration augmented by recent work of researchers from the Geological Survey of Canada, Athabasca University, the Universidad Nacional Autónoma de México, and the Universidad Autónoma de Yucatán. These recently acquired data were taken to map out detailed crater structure. All data were gridded at 750 m intervals before the horizontal gradient was computed. Most of the concentric gradient features can be related to inferred structural elements of the buried crater, including the central uplift (note the radial features revealed in the uplift), the collapsed transient cavity edge, faults in the zone of slumping, and the edge of the topographic basin - the now buried crater.

White dots represent the locations of water-filled sinkholes (solution collapse features common in the limestone rocks of the region) called cenotes after the Maya word dzonot. A dramatic ring of cenotes is associated with the largest peripheral gravity gradient feature. The cenotes of the ring are typically larger than those found elsewhere on the peninsula. The sinkholes developed when sea level was lower during the Pleistocene glaciation, becoming water-filled when sea level returned to its present level. The ring represents a zone of high permeability where groundwater can flow to the sea creating coastal freshwater springs at the east and west sides of the crater. The origin of the cenote ring remains uncertain, although the link to the underlying buried crater seems clear. The cenotes of the ring are developed in near-surface Tertiary limestones overlying the crater, and are not directly related to the rocks of the crater. Somehow the crater is able to reach up through several hundred metres of sediment, and tens of millions of years of time, to influence groundwater flow. Some form of subsidence controlled by peripheral structure of the crater may have induced fracturing in the much younger rocks that cover the crater. The fracturing could then initiate the groundwater flow that caused the cenotes to form. This subsidence may be continuing today. Note that the crater is able to influence modern erosion of the sediments that bury it. The edges of the crater correspond to a notch in the coastline in the east, and to a sharp bend southwards in the west. Also, the cenote ring corresponds to a topographic low of up to 5 metres along much of its length. (Image courtesy Geological Survey of Canada)

Horizontal gradient map of the Bouguer gravity anomaly over the Chicxulub crater (North is up.). The coastline is shown as a white line. A striking series of concentric features reveals the location of the crater. This image was constructed from gravity measurements taken by Petróleos Méxicanos beginning in 1948 in the course of petroleum exploration augmented by recent work of researchers from the Geological Survey of Canada, Athabasca University, the Universidad Nacional Autónoma de México, and the Universidad Autónoma de Yucatán. These recently acquired data were taken to map out detailed crater structure. All data were gridded at 750 m intervals before the horizontal gradient was computed. Most of the concentric gradient features can be related to inferred structural elements of the buried crater, including the central uplift (note the radial features revealed in the uplift), the collapsed transient cavity edge, faults in the zone of slumping, and the edge of the topographic basin - the now buried crater.

White dots represent the locations of water-filled sinkholes (solution collapse features common in the limestone rocks of the region) called cenotes after the Maya word dzonot. A dramatic ring of cenotes is associated with the largest peripheral gravity gradient feature. The cenotes of the ring are typically larger than those found elsewhere on the peninsula. The sinkholes developed when sea level was lower during the Pleistocene glaciation, becoming water-filled when sea level returned to its present level. The ring represents a zone of high permeability where groundwater can flow to the sea creating coastal freshwater springs at the east and west sides of the crater. The origin of the cenote ring remains uncertain, although the link to the underlying buried crater seems clear. The cenotes of the ring are developed in near-surface Tertiary limestones overlying the crater, and are not directly related to the rocks of the crater. Somehow the crater is able to reach up through several hundred metres of sediment, and tens of millions of years of time, to influence groundwater flow. Some form of subsidence controlled by peripheral structure of the crater may have induced fracturing in the much younger rocks that cover the crater. The fracturing could then initiate the groundwater flow that caused the cenotes to form. This subsidence may be continuing today. Note that the crater is able to influence modern erosion of the sediments that bury it. The edges of the crater correspond to a notch in the coastline in the east, and to a sharp bend southwards in the west. Also, the cenote ring corresponds to a topographic low of up to 5 metres along much of its length. (Image courtesy Geological Survey of Canada)

http://miac.uqac.ca/MIAC/chicxulub.htm -->

grav-3.jpg

Impact Energy Versus Frequency

http://www.unb.ca/passc/ImpactDatabase/--> http://www.unb.ca/passc/ImpactDatabase/essayimages/nucwin.gif

http://en.wikipedia.org/wiki/Torino_scale

CERTAIN COLLISIONS (red)

8. A collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if offshore. Such events occur on average between once per 50 years and once per several 1000 years.

9. A collision is certain, capable of causing unprecedented regional devastation for a land impact or the threat of a major tsunami for an ocean impact. Such events occur on average between once per 10,000 years and once per 100,000 years.

10. A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean. Such events occur on average once per 100,000 years, or less often.

CERTAIN COLLISIONS (red)

8. A collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if offshore. Such events occur on average between once per 50 years and once per several 1000 years.

9. A collision is certain, capable of causing unprecedented regional devastation for a land impact or the threat of a major tsunami for an ocean impact. Such events occur on average between once per 10,000 years and once per 100,000 years.

10. A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean. Such events occur on average once per 100,000 years, or less often.

The current record for highest Torino rating is held by 99942 Apophis, a 400m near-Earth asteroid. On December 23, 2004, NASA's Near Earth Object Program Office announced that Apophis (then known only by its provisional designation 2004 MN4) was the first object to reach a level 2 on the Torino Scale, and it was subsequently upgraded to level 4. It is now expected to pass the Earth on April 13, 2029 quite closely but with no possibility of an impact. Future uncertainties in the orbit of Apophis will occur because of gravitational deflection during the 2029 encounter, so a Torino rating of 1 (for an encounter in 2036) applied until August 2006, when Apophis was downgraded to 0.

Prior to Apophis, no NEO had ever been given a Torino value higher than 1. In February 2006, the rating for 2004 VD17 was upgraded to a value of 2 due to a possible encounter in the year 2102, making it the second asteroid to ever be given a Torino scale value higher than 1. Additional observations of 2004 VD17 resulted in a downgrade to 0.

http://en.wikipedia.org/wiki/Torino_scale

SPACEGUARD URLs

Lincoln Near-Earth Asteroid Research (LINEAR) Lincoln Near-Earth Asteroid Research (LINEAR)

http://www.ll.mit.edu/LINEAR/ Near-Earth Asteroid Tracking (NEAT)

http://neat.jpl.nasa.gov/ Spacewatch

http://pirlwww.lpl.arizona.edu/spacewatch/ Lowell Observatory Near-Earth Object Search (LONEOS)

http://asteroid.lowell.edu/asteroid/loneos/loneos.html Catalina Sky Survey

http://www.lpl.arizona.edu/css/ http://msowww.anu.edu.au/~rmn/

Japanese Spaceguard Association (JSGA) http://www.spaceguard.or.jp/ja/index.html

Asiago DLR Asteroid Survey (ADAS) http://planet.pd.astro.it/planets/adas/index.html

how to divert a NEO ?

Asteroid Tug

• “lands” on asteroid• secured with guy wires

• periodically fires engine when asteroid rotates to desired direction

• long term effort

http://www.b612foundation.org/papers/AT-GT.pdf

Gravity Tug

• massive ship

• gravity as towline

• long duration low level ion thrust

• no direct contact, physical proproperties of NEO unimportant

GRAVITY TUG http://antwrp.gsfc.nasa.gov/apod/ap051110.html

mass driver cargo ship uses part of payload as reaction mass

http://www.nas.nasa.gov/About/Education/SpaceSettlement/spaceres/illus.html