Task Force Report

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��Task Force Report: Annex A

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CHRONOLOGY

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4.5 billion years ago, the Earth was formed from material like that of asteroids and comets; and has been bombarded by Near Earth Objects (NEOs) ever since. Annex B gives specific examples of past impacts on the Earth and some recent near misses. This annex summarises the history of human understanding of asteroids and comets over the last three centuries.

Year	Event
1694	Edmond Halley suggests that cometary impacts may have caused global catastrophes, formed the Caspian Sea as an impact crater, and might be linked to the biblical flood legend. This idea revived from time to time (for example by William Whiston)
1790s	Pierre Simon de Laplace suggests comet impacts cause terrestrial catastrophes
1794	Chladni proposes that meteorites are of extra-terrestrial origin
1801	First asteroid discovered (Ceres); discovery of more Main Belt asteroids soon follows
1822	Lord Byron suggests that mankind could save itself from comet collisions by diverting them.
1890s	Alexander Bickerton suggests that impacts have sculpted the face of the Earth. Barringer suggests the �Meteor� Crater in Arizona is of impact origin
1898	Eros, first Earth-approacher discovered (Amor type asteroid)
1930s	Odessa crater in Texas shown to be an impact crater: the first proven case on Earth
1932	First two Earth-crossing asteroids discovered, Apollo and Adonis
1937	Asteroid Hermes (1937 UB), size about 800m, observed for only a few days as it misses Earth by just 670,000 kilometres (60 per cent further than Moon). Insufficient data obtained to secure orbit, so Hermes is lost; it may come back close to Earth at any time.
1941	Fletcher Watson estimates rate of impacts on Earth
1947	Minor Planet Center established by the International Astronomical Union (IAU) in Cincinnati, Ohio; moves to Cambridge Massachusetts, 1978
1948-51	Edgeworth (1948) and Kuiper (1951) predicted belt of comets, just beyond Neptune, much nearer Sun than Oort cloud. Now known as Edgeworth-Kuiper Belt
1949	Ralph Baldwin explains lunar craters as being of impact origin.
1949	Icarus, a close Earth-approacher discovered (Apollo type asteroid)
1950	Oort cloud hypothesis; billions of comets in spherical shell around solar system, 50,000 AU from Sun
1951	Ernst �pik (Armagh), after earlier work, estimates cratering rates on Earth
1954	First Aten-type �Inner-Earth� asteroid discovered (1954XA) but subsequently lost
c. 1960	Eugene Shoemaker proves impact origin of Barringer (Meteor) Crater (Arizona).
1970	Eleanor Helin (JPL) and Eugene and Carolyn Shoemaker start systematic photographic survey of NEOs
1973	Arthur C Clarke coins term Spaceguard in his novel �Rendezvous with Rama�
1979	Movie Meteor is released
before 1980	Nuclear winter calculations in context of full nuclear war: subsequently realised to be applicable to consequences of an NEO impact
1980	Alvarez et al propose that a massive asteroid impact led to the extinction of the dinosaurs. Later linked to event at Chicxulub
1981 July	NASA conference: Collision of Asteroids and Comets with Earth: Physical and Human consequences
1981	�Spacewatch�: Tom Gehrels and Bob McMillan, University of Arizona, began programme to survey NEOs including small asteroids, with electronic detection and data collection. Survey began late 1988
1990 Sept	US Congress House in NASA Multiyear Authorisation Act of 1990: �imperative that detection rate of Earth-orbit-crossing asteroids must be increased substantially, and that means to destroy or alter the orbits� should be defined and agreed internationally�
1990	American Institute of Aeronautics and Astronautics makes recommendations concerning NEOs to US Congress
1990	Duncan Steel�s survey of asteroids begins using United Kingdom Schmidt Telescope in Australia
1991	US Congress House Committee on Science and Technology use NASA Authorisation Bill to direct NASA to study 1) a programme to increase detection rate of Earth-orbit-crossing asteroids addressing costs, schedule, technology and equipment (Spaceguard Survey Report); 2) systems and technologies to destroy or alter orbits of such asteroids if they should pose a danger to life on Earth (NEO Interception Workshop)
1992 Jan	Spaceguard Survey Report delivered to US Congress. Recommends a search programme and international collaboration to find greater than 1 kilometre objects; and the provision of six ground based telescopes, northern and southern hemisphere sites, southern hemisphere radar; half costs to come from international partners
1992 Jan	NEO Interception Workshop. Full investigation of counter-measures concluded that nuclear explosives in stand-off mode most likely to succeed (see 1991 above)
1992 March	Three witnesses testify before US Congress on results of above workshops
1993	European Science Foundation initiates new scientific network �Impact Cratering and Evolution of Planet Earth�
1994 Feb	US Congress House Committee on Science and Technology pass an amendment to NASA Authorisation Bill directing NASA to report within a year with a programme to identify and catalogue, with help from the Department of Defense and space agencies of other countries, within 10 years, orbital characteristics of all comets and asteroids greater than 1 kilometre diameter and in an orbit that crosses Earth�s
1994 July	Shoemaker-Levy 9 comet collides with Jupiter. At least 21 cometary fragments, with diameters up to 2 kilometres, cause massive explosions and spark public interest
1994	IAU�s 22nd Assembly�s Working Group on NEOs, present a report recommending that an international authority should take responsibility for NEO investigations
1995 June	Near Earth Objects Survey Workgroup Report is released with a programme to meet Congress� requirements. Recommends NASA, USAF and international collaboration; two dedicated 2 metre discovery telescopes; use of two existing 1 metre telescopes for survey and follow-up; enhanced funding to obtain roughly half time on a 3 to 4 metre telescopes for physical observation; MPC enhancements
1995	UN host conference on NEOs attended by representatives of UN Office of Outer Space Affairs
1995	IAU�s Working Group on NEOs workshop sets up the Spaceguard Foundation to promote international NEO discovery, follow-up and study.
1996 Jan	UN meeting in Colombo, Sri Lanka, resolves that an international network of telescopes under UN aegis is needed for NEO searching and tracking
1996	Parliamentary Assembly of the Council of Europe, Resolution 1080, detection of asteroids and comets that are potentially dangerous to mankind
1997	Spaceguard UK set up to promote British NEO activities
1998	Two new major NEO search programmes start in United States using Department of Defense facilities: NEAT in Hawaii and LINEAR in New Mexico � see Annex C � leading to step-increase in NEO discovery rate
1998	National Research Council of US National Academy of Sciences: highest priorities to NEOs
1998 May	US Congressional Hearings on NEOs and Planetary Defense. Recommends use of more GEODSS telescopes, states difficulties with using already existing observatories
1998	NASA NEO Program Office set up at JPL to help co-ordinate and provide a focal point for US studies of NEOs
1998 Jul-Aug	Armageddon and Deep Impact films released, both about NEO collision with the Earth
1999	In a report to the ESA Council at Ministerial level, ESA�s Long Term Policy Committee recommend that the Agency be involved in NEO activities, including the study of countermeasures
1999 March	Threat from NEOs is debated in House of Commons. Minister for Energy and Industry, John Battle, says that government will consult British astronomers and other experts on ways the UK can support NEO research
1999 June	Threat from NEOs discussed in House of Lords. Science Minister, Lord Sainsbury, says that Britain must co-operate internationally on this topic
1999 June	International Monitoring Programs for Asteroid and Comet Threat (IMPACT) conference in Italy organised by the IAU, the Spaceguard Foundation and others. Outcomes include the �Torino Scale� to describe risk and severity of possible impact for newly discovered objects.
1999 July	UNISPACE III, a UN Space conference, hold a workshop on NEOs and make recommendations to UN General Assembly. Subsequently, resolution adopted by conference, the Vienna Declaration on Space and Human Development, declares a strategy including actions that should be taken to improve knowledge of NEOs; improve international coordination of activities relating to NEOs; harmonise worldwide effort to identify, follow up and predict NEO orbits; and research safety measures on the use of nuclear power sources in outer space
2000 September	Report of the UK Government Task Force on Potentially Hazardous NEOs is published.

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Chapter 1 Introduction

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