1. Asteroids & Meteorites: The Hazards to Life
13 March 2018

2. Asteroids
Apollo
Trojans

3. Asteroid Belt as viewed from Above
Over 100,000 objects greater than 10 km. now identified in the Main Belt
Total mass less than 1% of moon’s mass
Over 100 NEAs greater than 1 km. across are being tracked; probably part of a population of about 2000
Kirkwood gap (and others) occur in the belt where there are orbital resonances with Jupiter
Asteroids classified by ‘spectral group

4. Kirkwood Gaps

5. S Asteroids (‘silicaceous’)
951 Gaspra 433 Eros (true color) Ida (and Dactyl)
19 x 12 x 11 km x 13 x13 km 58 x 23 km (1km)
Galileo flyby, NEAR orbit/landing Galileo flyby, 1993
Grooves, curved near-Earth asteroid, member of Koronis
depressions, ridges space weathering family, first ID of
(Phobos-like) effects documented asteroid ‘moons’

6. C Asteroids (‘carbonaceous’)
253 Mathilde; 66 x 48 x 46 km, visited by NEAR Shoemaker
Surface as dark as charcoal; typical outer belt asteroid

7. Ida and Dactyl

8. Itokawa

9. Hyabusa samples Itokawa

10. Hyabusa
Returns
June 2010

11. Steins 2008

12. Toutatis Model

13. Vesta, Ceres, Moon

14. Dawn Mission at Vesta

16. Vesta Craters

17. Asteroids Summary
Solid objects mostly in a belt between Mars and Jupiter
Small bodies much more common than larger ones
Classes similar to meteorites: Stony (S), Carbonaceous (C), Metallic (M)
Bodies and belts shaped by collisions, resonances with Jupiter
Source of meteorites

18. Meteorites

20. Chondrite

21. Achondrite

22. Martian

23. Jackson Hole Fireball, August 10, 1972

24. Hoba Iron 3m x 2m x 1m; 60+ tons Found 1920, Namibia
No crater, classified ataxite

25. Ordinary Chondrites (from S Asteroids?)

26. Three Views of Vesta Hubble image, model and color-shaded topography
Largest member of V class of asteroids (vestoids)
Spectral variations consistent with HED meteorites

27. Meteor showers Time exposure image, tracking stellar motion
Stars stay still, meteorites make trails

28. The Peekskill (NY) Fireball

29. P Jenniskens et al. Nature 458, 485-488 (2009)
Macroscopic features of the Almahata Sitta meteorite.
P Jenniskens et al. Nature 458, (2009)

30. Chondrites Rocky, inhomogeneous, contain round “chondrules”
Microscope image

31. Iron meteorites: from core of differentiated asteroids

32. Stony-Iron meteorites - the prettiest
Crystals of olivene (a rock mineral) embedded in iron
From boundary between core and mantle of large asteroids?

33. Sutter’s Mill fell and found in 2012

36. The main points: Meteorites
Each year the Earth sweeps up ~80,000 tons of extraterrestrial matter
Some are identifiable pieces of the Moon, Mars, or Vesta; most are pieces of asteroids
Meteorites were broken off their parent bodies 10’s to 100’s of million years ago (recently compared to age of Solar System)
Oldest meteorites (chondrites) contain interstellar dust, tiny diamonds made in supernova explosions, organic molecules and amino acids (building blocks of life)
Direct insight into pre-solar system matter, solar system formation

37. Asteroid Hazard: The Death of the Dinosaurs

38. Tunguska, Siberia, June 30, 1908
Black and white photos taken during field expedition in 1927; color photo taken in 1990

39. Potentially Hazardous Asteroid Threat Size-frequency diagram for impacting objects
~100 tons of meteroritic dust falls each day
50 m impactor once per 1000 yr (local effects)
500 m impactor once per million years (regional effects)
5 km. impactor once per 100 million years (global effects)

41. Plot of orbits of known potentially hazardous asteroids, with over 140 meters in size and passing within 7.6 million kilometers of Earth

42. Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth.
Specifically, all asteroids with an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 au or less and an absolute magnitude (H) of 22.0 or less are considered PHAs.
In other words, asteroids that can't get any closer to the Earth than 0.05 au (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 140 m (~500 ft) are not considered PHAs.

43. Potentially Hazardous Asteroids

45. While the chances of a major collision are not great in the near term, there is a high probability that one will happen eventually unless defensive actions are taken. Recent astronomical events—such as the Shoemaker-Levy 9 impacts on Jupiter and the 2013 Chelyabinsk meteor along with the growing number of objects on the Sentry Risk Table—have drawn renewed attention to such threats. NASA warns that the Earth is unprepared for such an event.

46. Asteroid impact avoidance
Asteroid impact avoidance comprises a number of methods by which near earth objects (NEO) could be diverted, preventing destructive impact events. A sufficiently large impact by an asteroid or other NEOs would cause, depending on its impact location, massive tsunamis, multiple firestorms and an impact winter caused by the sunlight-blocking effect of placing large quantities of pulverized rock dust, and other debris, into the stratosphere.

49. A collision between the Earth and an approximately 10-kilometer-wide object 66 million years ago is thought to have produced the Chicxulub Crater and the K-T extinction event, widely held responsible for the extinction of most dinosaurs.

50. Chicxulub, Yucatan penninsula, Mexico
Gravity map of buried structure
180 miles across; 65 millions years old
Identified in early 1990s with seismic data, after 10 year ‘search’

52. Toutatis

53. How Do We Mitigate the Hazard of Possible Asteroid Impacts?
Efforts to mitigate the hazard of possible asteroid impacts with Earth include:
asteroid deflection mission concept studies,
impact effects studies,
and emergency response planning.
NASA’s NEO Observations Program is sponsoring several studies of techniques for impact mitigation. The European Union’s NEOShield Project is conducting a detailed analysis of “open questions relating to realistic options for preventing the collision of a NEO with the Earth.”

54. NEOShield is considering kinetic impactor options, blast deflection techniques, and gravity-tractor methods. Impact effects studies are ongoing at some of the Department of Energy’s national laboratories.
Impact emergency response planning: NASA’s Near Earth Object Observations (NEOO) Program has participated in impact-response planning activities with the U.S. Air Force, the Defense Advanced Research Projects Agency, and the Federal Emergency Management Agency (FEMA). NASA and FEMA have formed a working group on impact emergency response planning. 

57. Asteroid Mining

60. Economics
Currently, the quality of the ore and the consequent cost and mass of equipment required to extract it are unknown and can only be speculated. Some economic analyses indicate that the cost of returning asteroidal materials to Earth far outweighs their market value, and that asteroid mining will not attract private investment at current commodity prices and space transportation costs. Other studies suggest large profit by using solar power. Potential markets for materials can be identified and profit generated if extraction cost is brought down. For example, the delivery of multiple tons of water to low earth orbit for rocket fuel preparation for space tourism could generate a significant profit if space tourism itself proves profitable, which has not been proven

62. In 1997 it was speculated that a relatively small metallic asteroid with a diameter of 1.6 km (1 mi) contains more than US$20 trillion worth of industrial and precious metals. A comparatively small M-type asteroid with a mean diameter of 1 km (0.62 mi) could contain more than two billion metric tons of iron-nickel ore, or two to three times the world production of 2004. The asteroid 16 Psyche is believed to contain 1.7×1019 kg of nickel–iron, which could supply the world production requirement for several million years. A small portion of the extracted material would also be precious metals.

65. Not all mined materials from asteroids would be cost-effective, especially for the potential return of economic amounts of material to Earth. For potential return to Earth, platinum is considered very rare in terrestrial geologic formations and therefore is potentially worth bringing some quantity for terrestrial use. Nickel, on the other hand, is quite abundant and being mined in many terrestrial locations, so the high cost of asteroid mining may not make it economically viable

67. Financial feasibility
Space ventures are high-risk, with long lead times and heavy capital investment, and that is no different for asteroid-mining projects. These types of ventures could be funded through private investment or through government investment. For a commercial venture it can be profitable as long as the revenue earned is greater than total costs (costs for extraction and costs for marketing).The costs involving an asteroid-mining venture have been estimated to be around US$100 billion.
There are six categories of cost considered for an asteroid mining venture:
Research and development costs
Exploration and prospecting costs
Construction and infrastructure development costs
Operational and engineering costs
Environmental costs
Time cost

68. Summary: Asteroid Mining
Due to the high launch and transportation costs of spaceflight, inaccurate identification of asteroids suitable for mining, and in-situ ore extraction challenges, terrestrial mining remains the only means of raw mineral acquisition today. If space program funding, either public or private, dramatically increases, this situation is likely to change in the future as resources on Earth are becoming increasingly scarce and the full potentials of asteroid mining are researched in greater detail.[However, it is yet uncertain whether asteroid mining will develop to attain the volume and composition needed in due time to fully compensate for dwindling terrestrial reserves.