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Facing up to the risks

of impacts of Near-

Earth Objects

Debbie Lewis MSc FEPS

We may never encounter a natural disaster more violent than a storm. And so we become complacent, relaxed, unconcerned. But in the history of nature, the record is clear. Worlds have been devastated. On the landscapes of other planets where the records of the past have been preserved, there is abundant evidence of major catastrophes. Even on the Earth, even in our own century, bizarre natural events have occurred (Sagan, 1981:92).

• What is the hazard?

• Sample cases

• What is everybody doing?

• What is ESA doing?

• Conclusions/questions

Outline

Meteorite (10 cm)

• Near-Earth Object (NEO): Any asteroid coming closer than 0.3 AU to the Earth

• 1 AU = Astronomical Unit = distance Sun-Earth = 149.6 Mio km

• Threatening object: Any asteroid that may hit the Earth

• Risk list: A list containing all threatening objects

Definitions/terminology

500 m

NEO Itokawa

(credit: JAXA)

Known number of Near Earth

Asteroids

Near Earth Objects population

(From JPL – NEO site)

Estimated Number of Asteroids and NEOs

(Data from NEODyS or JPL NEO site, Aug 2013)

• > 600 000 known Asteroids

• > 10 000 known NEOs

• > 400 NEOs in risk list (NEOs with small but non-zero impact probability within next 100 years)

• Estimated number of known NEOs:

– 90% of NEOs with diameter larger than 1 km (≥ 860 NEAs + 94 near-Earth Comets of a total of ≈ 1050)

– 15-25% of NEOs larger than 140 m (total ≈ 20,000 - 30,000)

– < 2.0% of NEOs larger than 30 m (total ≈ 500,000 - 1,000,000)

Most NEOs are still unknown!

NEO impacts: frequency and effects

• Asteroids (and Comets) hit Earth with very high velocities.

• typical: 10 - 20 km/s, 20 times faster than a gun bullet!

NEO diameter Impact energy

[Megatons TNT] (1g TNT ≡ 4184 J)

Typical interval [Years]

Effect

2 mm 1 per hour

(visible for each location)

Nice meteor

3 m 0.002 1 Fireball, Sudan Event, Meteorites reach ground

10 m 0.08 10 Big fireball, fear, shock wave, 5-fold energy of Hiroshima bomb

40 m 5 500 Tunguska explosion or Crater

140 m 220 10,000 Regional destruction, Tsunami

500 m 10,000 200,000 Europe-wide destruction

1 km 80,000 700,000 Millions dead, global effects

10 km 80 million 100 million End of human civilisation

Age (years) or date Impactor Size Location Consequences

1 K-T mass biota boundary

between Cretaceous and

tertiary geological periods 65

Million years ago

10-15km

diameter

asteroid or

comet

200km crater

discovered

Chicxulub,

Pueblo

Yucatan

Peninsula Gulf

of Mexico

Estimate extinction of 70% of

animal and plant species.

Penetrative tsunamis.

Cessation of photosynthesis and

climatic cooling

2 50,000 years ago Meteorite 150 ft

in diameter

Barringer

Crater Arizona

Creation of a crater 1 mile

across, 2.4 miles in

circumference and >550 ft in

depth

3 4,000 years ago Meteorite Kaali Crater,

Estonia

Formation of 100 m crater

NEO impacts: frequency and

effects

Tunguska

30 June 1908 - 105 years ago

2000 km2 of Taiga were destroyed in Siberia

Barwell Meteorite 24.12.65

Carancas, Peru

Crater with

14-m diameter

formed by

impact from

space in 2007.

Chelyabinsk Impact Event • Location: 55.2o N, 61.4o E (near Chelyabinsk, Russia)

• Date/time: 15 Feb 2013, 03:20 UT (09:20 LT)

• Diameter of object: 19 m, mass ≈ 12000 t

• Entry velocity: 18.6 km/s, entry angle: 20o from surface

• Total energy: equiv. to 480 kt TNT

• Altitude of main explosion: 30 – 25 km

• Max brightness of fireball: m ≈ -30 (about 30 x sun brightness)

• 7300 buildings damaged

• > 1500 people injured

• > 100 kg of meteorites found (usually small pieces, asteroid was ordinary chondrite)

• Asteroid could not be seen approaching (too close to sun direct.) and was too faint for prior detection during the last 10 years

Uncertainty

Uncertainty exists as to the extent of the scale of a NEO impact for six reasons: 1. The NEO population is not sufficiently

understood 2. Inability to determine impact levels for objects

between 50m and 140m in diameter 3. Unknown composition of NEOs 4. Variable collision effects 5. Effects may exceed local and regional areas and

have global effects 6. The size and type of NEO which would cause

these effects

Risk Treatment

Four risk treatment methods have been

identified to mitigate the NEO hazard:

•Characterisation

•Civil protection

•Planetary defence

•Establishment of a research programme

Current State of Preparedness

• Kinetic Impactor

• Gravity Tractor

• Nuclear Device

• Civil Protection

Evacuation or

Shelter?

Discussions Within UN COPUOS

• Action Team 14 of UN

COPUOS has

developed a response

strategy

• Adopted in Jun 2013

• Two groups are to be

installed:

– International Asteroid

Warning Network

(includes interface to

emergency response)

– Space Missions

Planning Advisory Group

Extant Guidance - UN System

• Increasing public awareness

• Obtaining commitment from public authorities

• Stimulating interdisciplinary and inter-sector

partnership and expanding risk-reduction

networking at all levels

• Enhancing scientific research of the causes

of natural disasters and the effects of natural

hazards and related technological and

environmental disasters on societies

The Spaceguard Centre

http://spaceguardcentre.com/

NEO Coordination Centre – ESRIN, Italy

SSA-NEO

Coordination Centre -

inaugurated 22 May

2013

The SSA-NEO web portal

• Federates some key

European assets:

– NEODyS = orbit

computation,

prediction, risk list

– Physical properties

database

– Priority list = showing

objects in need of

observations

http://neo.ssa.esa.int

2015 IAA Planetary Defense Conference:

Assessing Impact Risk & Managing Response

April 13-17th 2015

Frascati, Italy

http://www.pdc2015.org/