The search for Near Earth Objects (NEO) - Microplanets (comets, asteroids and meteoroids) that share our region of the solar system. Inspired by the work of Gene Shoemaker and a memorial lecture by Ken Russell from the Anglo Australian Observatory. The term Spaceguard was coined by Arthur C Clarke in his 1973 science fiction novel Rendezvous with Rama. The introduction has an uncanny September 11 coincidence. (Extract)
Tip: These pages are in
plain HTML. Try
Ctrl-F to "Find" any text you are interested in. Why so plain? - this page was started in 1997.
"No one wants to look back and
regret actions
not taken" - Dr David Suzuki, The Nature of Things.
'Many might say "But we
know of no one
that has ever died from an asteroid impact." That's true [in recent
times], but then who has ever died from a thermonuclear explosion?
Surely no one would claim that they are not dangerous?' - Arthur C
Clarke, Foreword to Rogue Asteroids and Doomesday Comets by Duncan
Steel.
"No one has ever been killed by a meteorite in the presence of a meteoritist and a medical doctor!" - John Lewis
Recent items are near the top (posting date shown).
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1972:
Rock
samples collected by Apollo 17 (the last manned mission to the Moon)
show that the age of the 85km diameter Tycho
Crater is about 100 million years.
An asteroid or comet about 4km across would be
needed to make a crater this size. On average the Earth is struck by a
microplanet this size every 10 million years. The impact rate on the
smaller Moon is about one tenth of
that on Earth so Tycho is within expectations (but see this note
about impacts randomly distributed in time).That is why this is an unofficial web-site - there is no Spaceguard Survey in Australia at the present time. The web site has been started to support the re-establishment of the Australian Spaceguard Survey and to provide links to other Spaceguard-related sites.
It is evident that the Australian
Government is only interested in short term issues and is
unlikely
to support a project which might not benefit mankind for decades, or
even centuries. One problem is that the bureaucracy does not have a
"pigeon hole" for this topic - it is not pure "science" and there is no
tangible enemy to make it a "defence" matter. Therefore the Australian
Spaceguard Survey will probably need
the support of individuals, corporations and societies.
We are not asking for money, but an indication of support - and to determine whether the web site is a suitable way to generate this support. See also the Guestbook.
1 April 1997 Canberra Times: "Asteroid watch might resume" - Sky watching for "killer rocks" in Australia could be resurrected after intervention by Prime Minister John Howard...Science Minister Peter McGauran said Mr Howard recently asked him, Education Minister Vanstane and Defeence Minister McLachlan to examine whether asteroid spotting should continue..."we're treating it as a case where individuals can fall between portfolios becuase they don't fit neatly in one or the other"...
Update March 1999: A glimmer of hope about Australian funding for Spaceguard: The Coordination Committee on Science and Technology (CCST) is a high level committee set up by the Government of the Commonwealth of Australia, comprising representatives of departments with an interest in or responsibility for science, technology and innovation matters. It lists "Near Earth Asteroids" under "Matters receiving attention in the current financial year"! . Copy here (for the record!)
Update 10
September 1999: After a three
year break a professional search for Earth-threatening
asteroids will soon begin again in Australia. The project is a
collaboration between astronomers at the University of Arizona and
the Australian National
University. It involves
refurbishing a telescope at Siding Spring in New South Wales and
providing a verysensitive electronic detector array, computer pointing
control and automatic detection software.
The project will help to fill a huge gap in our ability to
detect asteroids
which might collide with the Earth. Until now the only professional
searches
were in the Northern Hemisphere - the southern half of the sky was not
covered.
Early detection of a potentially threatening asteroids is essential if
mankind
is to have sufficient time
to mitigate the threat. Even the moderate rocket power we have
available today would be sufficient to deflect an asteroid away from a
collision, provided that the action can be
taken over decades and the asteroid is
given
a little nudge during each orbit around the Sun.
Although the ANU/UA project is a welcome development
renewed
government funding for an additional telescope will be required if the
goals of the international Spaceguard Survey are to be achieved. That
goal is to
discover, within a decade, 90% of Earth-approaching asteroids with a
diameter of 1 km or more. A collision by an asteroid of this size would
be a grave threat to our civilisation and the death toll would likely
be
in the hundreds of millions.
NASA NEO News - copy
of ANU/UA Press Release
18 Mar 02 OPINION - There was good coverage of the Spaceguard issue on Australian TV yesterday. Science Minister Peter McGauran tried to accuse NEO researchers of "fear-mongering" and being "self-indulgent" - a sure sign of an uncomfortable politician. In fact none of the 91 scientists from 17 countries who signed the letter to the Federal Government earlier this year would benefit in any way from an Australian decision to fund Spaceguard - other than the knowledge that a blind spot in the south would be eliminated. However, the reaction to the programs was overwhelmingly supportive and I think Mr McGauran should discuss this issue with his colleagues. He suggested Spaceguard would take 5% out of the $18 million budget for astronomy in Australia - a sneaky way to try and eliminate support for Spaceguard from other astronomers. We are saying it is not strictly science research and it would be more appropriate to fund it from the huge defence budget. If you agree please tell your local member of federal parliament.
1 Feb 02: In a
remarkable show of global
solidarity more than 90 scientists from 17 countries have signed a letter to Australian Prime Minister
John Howard, calling
for a major Australian
contribution to Spaceguard - the international
effort to
detect asteroids that might collide with the Earth. The signatories to
the letter come from Australia, Canary Islands, Croatia, Czech
Republic, Denmark, Germany, Greece, Israel, Italy, Poland, Romania,
Russia, Spain, Sweden, Ukraine, United Kingdom and United
States
of America. They include leading asteroid researchers such as David
Levy and Caroline Shoemaker - famous for discovering Comet
Shoemaker Levy 9 that collided with Jupiter in 1994. The
letter was
organised by Jay Tate from the Spaceguard
Centre in the UK and Dr Benny Peiser from Liverpool John
Moores
University, UK.
Michael Paine from the Planetary Society Australian Volunteers assisted
them. A PDF copy of the letter and press release can
be viewed at http://www4.tpg.com.au/users/tps-seti/pr_oz_sg.pdf.
Updates:
Space.com World's
Asteroid Hunters Make Political Plea to
Save Earth. Recipient list added to PDF
document.
5 Feb 02 Canberra Times: Australia
fails world on asteroids: scientists.
The Risk and Consequences of Asteroid/Comet Impact
The following table is based on data from the NEO weblinks and you are encouraged to follow those links for a more complete picture. There are some inconsistancies between these links due, in part, to a lack of observational information (which would be corrected by a full Spaceguard survey). Therefore the table is very approximate but it will give some idea of the threat posed by asteroid and comet impacts.
| Very approx size of object * | Equiv. Megatons of TNT ("Bravo" H bomb=15Mt) |
Odds in 50 years # | Consequences @ |
| 10 metres | 20 kilotons | Annual | "Fireballs" burn up in atmosphere. Local hazard from debris and shockwaves. Possible trigger for nuclear warning systems. Smaller objects in much greater numbers pose a threat to spacecraft |
| 100m | 75 megatons | Earth:1 in 20 Inhabit:1 in 160 |
Meteor crater, Wolfe Crater, Tunguska. Local direct destruction (eg 50km radius). Around 1 million fatalities. |
| 500m | 10,000 | Earth:1 in 800 Inhabit:1 in 3,600 |
Regional destruction. Short-term global climate (and economic) effects. Tsunami (tidal waves) devastate coastal areas. Around 35 million fatalities. |
| 1km | 100,000 | Earth:1 in 2,000 Inhabit:1 in 6,000 |
Medium-term global climate effects. Around 63 million fatalities. |
| 2 km | 1 million | Earth: 1 in 20,000 Inhabit: 1 in 30,000 |
Global catastrophe threshold. Severe long-term climate effects. Collapse of agriculture. Around 1500 million fatalities. |
| 10km | 100million | Earth:1 in 2 million Inhabit:same! |
K-T impact. Mass extinction (eg dinosaurs) |
These values are based on the estimated NEO population. Care should be taken when comparing the "odds in 50 years" with actual evidence of impacts with the Earth. See Poisson Distributions.
Update
25 Nov 04 Icarus
(abstract): Bias-corrected
population, size distribution, and impact hazard for the near-Earth
objects - Globally
destructive collisions (~1021 J) of asteroids 1 km or larger strike the
Earth once every 0.60±0.1 Myr on average. Regionally
destructive
collisions with impact energy greater than 4×1018 J (~200 m
diameter)
strike the Earth every 56,000±6000 yr. Collisions in the
range
of the
Tunguska event (4-8×1016 J) occur every 2000-3000 yr. This
latest
analysis suggests that the odds shown in the above table improve by
about 5 times for 1km objects and less.
Another way of looking at the risk posed by asteroid/comet impact is to compare the chances of dying from selected causes. This table is based mostly on a paper by Clark Chapman and David Morrison and is for residents of the USA:
| Cause of death | Chances |
| Motor vehicle accident | 1 in 100 |
| Homicide | 1 in 300 |
| Melanoma (a skin cancer*) | 1 in 300 |
| Fire | 1 in 800 |
| Firearms accident | 1 in 2,500 |
| Electrocution | 1 in 5,000 |
| Asteroid/comet impact | 1 in 20,000# |
| Passenger aircraft crash | 1 in 20,000 |
| Flood | 1 in 30,000 |
| Tornado | 1 in 60,000 |
| Venomous bite or sting | 1 in 100,000 |
| Food poisioning by botulism | 1 in 3 million |
In other words, a US resident is 200 times more likely to die in car
crash than from a NEO impact and 5 times more
likely to die
from a NEO impact than a venemous bite or sting.
Note that although an asteroid/comet impact is a very rare event, the number of people likely to be killed is greatly in excess of the other causes in the table. Compare the national US expenditure on "prevention" for all of these causes and it is evident that asteroid/comet detection is grossly under-funded.
For people living in low-lying coastal areas on the shoreline of deep oceans the risk could be several times greater due to the extra risk of tsunami.
.![[asteroid]](ast1-5km.jpg)
Note: I have cheated with this picture - it is actually asteroid Ida which is 50km across - you will have to imagine it is only 1km (in fact the small dot to the right is a 1km companion asteroid "Dactyl"). Thank you to Dr. Christian Gritzner from EUROSPACE GmbH for pointing this out!
NEO Web Links has moved (getting too large for this page!)
The worldwide Spaceguard program should be able to detect several thousand "candidate" asteroids/comets over a fifteen year period for less than US$10 million per year. Compared with worldwide defence expenditure, and space exploration budgets, this is very cheap "insurance" for mankind!
Media Contacts
Since there is no Australian Spaceguard Survey at
present
general media inquiries in Australia should be
directed to research organisations such as
the Anglo-Australian
Observatory (phone Sydney 02 93724800) or Mt Stromlo(Canberra
02 6249 0230)
or the links at ASTRONOMICAL
SOCIETY OF AUSTRALIA. We will, however, try and answer email enquiries
about matters
covered on this web site.
Update May 2013: Astronomer and author Duncan Steel now has a website.
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The Planetary Society
Australian Volunteer
Co-ordinators or the Planetary Society
Started in 1997 (when web page names were limited to 8 letters). For last update see News