Apophis and the Keyhole

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Apophis and the Keyhole

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SOLAR SYSTEM

• sun
• planets, dwarf planets, and moons
• asteroids and comets
• dust
• lots of space between everything

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Bob Perry http//www.cfa.harvard.edu/iau/lists/In
nerPlot.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-a
rc 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.
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http//neo.jpl.nasa.gov/orbits/ gt select Apophis
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• Apophis is about three times the size of the
  asteroid that made 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

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mathematical model
. . . changes in the 17th significant digit,
rounded and truncated by typical computing
systems, make the difference between an Apophis
hit or a miss by one Earth radius. That is, even
computational noise in the hardware doing the
calculation, never mind the measurement and
physical error sources that will always exist, is
an issue. Jon Giorgini CCNet 40/07
- 21 February 2007
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asteroid 1997 XF11 early model 2028 flyby 18
month year
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asteroid 1997 XF11 model with precovery data 202
8 flyby
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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 --gt
grav-3.jpg
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Impact Energy Versus Frequency
http//www.unb.ca/passc/ImpactDatabase/--gt
http//www.unb.ca/passc/ImpactDatabase/essayimages
/nucwin.gif
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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.
http//en.wikipedia.org/wiki/Torino_scale
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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
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SPACEGUARD URLs
Lincoln Near-Earth Asteroid Research (LINEAR)
http//www.ll.mit.edu/LINEAR/ Near-Earth
Asteroid Tracking (NEAT) http//neat.jpl.nasa.go
v/ Spacewatch http//pirlwww.lpl.arizona.edu/sp
acewatch/ Lowell Observatory Near-Earth Object
Search (LONEOS) http//asteroid.lowell.edu/aster
oid/loneos/loneos.html Catalina Sky Survey
http//www.lpl.arizona.edu/css/
http//msowww.anu.edu.au/rmn/ Japanese
Spaceguard Association (JSGA) http//www.spacegu
ard.or.jp/ja/index.html Asiago DLR Asteroid
Survey (ADAS) http//planet.pd.astro.it/planets/
adas/index.html
Lincoln Near-Earth Asteroid Research (LINEAR)
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how to divert a NEO ?
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Asteroid Tug

• lands on asteroid
• secured with guy wires
• periodically fires engine when asteroid
  rotates to desired direction
• long term effort

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http//www.b612foundation.org/papers/AT-GT.pdf
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Gravity Tug

• massive ship
• gravity as towline
• long duration low level ion thrust
• no direct contact, physical proproperties of
  NEO unimportant

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GRAVITY TUG http//antwrp.gsfc.nasa.gov/apod/
ap051110.html
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mass driver cargo ship uses part of payload as
reaction mass
http//www.nas.nasa.gov/About/Education/SpaceSettl
ement/spaceres/illus.html