1. Asteroids & Meteorites: The Hazards to Life
Ganna (Anya) Portyankina 11 March 2019

2. First, some definitions:
Asteroids are minor planets.
A meteorite is a piece of rock from outer space that strikes the surface of the Earth.
A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to one- meter-wide objects. Objects smaller than this are classified as micrometeoroids or space dust.
A meteor is a small body of matter from outer space that enters the earth's atmosphere, becoming incandescent as a result of friction and appearing as a streak of light.
First, some definitions:

3. Plan:
Asteroids
Meteorites
Asteroids hazards
Asteroid mining

4. Asteroids
On 11 February 1801 Giuseppe Piazzi (a Catholic priest at the Academy of Palermo, Sicily) discovered Ceres – the first known body in the region between Mars and Jupiter that we now call an asteroid belt.
In just several years astronomers discover so many of similar bodies that it became obvious that they are a new kind of planetary bodies .
We now classify Ceres as a minor planet (D = 945 km).
Fun fact: After discovery, at the end of 1801 they have lost Ceres, because the methods to predict its orbit were too rough. To recover Ceres, Carl Friedrich Gauss, then 24 years old, developed an efficient method of orbit determination and calculated its new location that was observationally confirmed.
Image from Dawn mission.

5. Asteroids belt Over a half-million asteroids
Over 100,000 objects greater than 10 km
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
Three classes:
S-type (for stony)
C-type (chondrites or carbonaceous, largely composed of carbon, the most common— and perhaps the oldest—of the bunch)
M-type (metallic).
Some asteroids have moons
There are, on average, 620,000–1.8 million miles between asteroids
Asteroids are like snowflakes - no two are exactly alike
Asteroids belt

6. Kirkwood gap (and others) occur in the belt where there are orbital resonances with Jupiter

7. 951 Gaspra The Galileo spacecraft was the first planetary mission to photograph an asteroid "up-close".
Galileo flyby

8. 243 Ida and Dactyl
Galileo flyby

9. 433 Eros and Mathilde
Flyby by NEAR

10. Bennu

11. 25143 Itokawa

12. Ryugu

13. Steins (~7 km) and Letitia (100 km)

15. Missions dedicated to asteroid studies:
NEAR
Dawn spacecraft
OSIRIS-Rex
Hayabusa
Hayabusa 2
(Rosetta)
Psyche (plan)
Lucy (plan)
Eros
Vesta and Ceres
Bennu
25143 Itokawa
Ryugu
(flew by 2867 Steins and 21 Lutetia)
16 Psyche
five Trojan asteroids

16. 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

17. Meteorites Types: Iron Stony-iron (Pallasites and Mesosiderites)
Stony (Chondrites and Ahondrites)

18. Iron meteorites are mainly made of an iron-nickel alloy with a distinctive crystalline structure known as a Widmanstätten texture.

19. Iron meteorites come from core of differentiated asteroids

20. Stony-iron meteorites consist of almost equal parts iron-nickel metal and silicate minerals including precious and semi-precious gemstones.
Pallasites are thought to be samples of the boundaries between a metal core and the silicate, olivine-rich mantle around it.
Mesosiderites form when debris from a collision between two asteroids is mixed together.
Pallasites contain big, beautiful olive- green crystals - a form of magnesium- iron silicate called olivine - embedded entirely in metal.
Mesosiderite meteorites are breccias, a variety of rock composed of broken fragments of minerals or rock cemented together by a finer material.

21. Stony meteorites: consist mostly of silicate minerals
Stony meteorites: consist mostly of silicate minerals. There are two main types of stony meteorite:
Chondrites have a distinctive appearance, made from droplets of silicate minerals mixed with small grains of sulphides and iron-nickel metal. Their millimetre-sized granules give chondrites their name, from the Greek 'chondres' meaning sand grains.
When magma cools and crystallises, it creates a concentric layered structure. This process is known as igneous differentiation.
Chondrites - most primitive and pristine rocks in the solar system and have never been melted
Achondrites (including meteorites from asteroids, Mars and the Moon) - igneous, meaning at some point they were melted into magma.

22. Meteorites, summary:
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

23. Asteroids hazards

24. Meteor showers Time exposure image, tracking stellar motion
Stars stay still, meteorites make trails
The Peekskill Bolide Fireball fell over the skies of the United States at about 7:50pm, on Friday, October 9th, The smashed Malibu is the victim of the remaining meteorite which struck the earth.

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

26. 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)

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

29. Chelyabinsk meteor, February 15 2013

30. Extreme low probability – high impact hazard
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.

31. Meteor crater: diameter = 1.186 km caused by impactor = 50 m
Meteor crater in AZ

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

33. 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 Near Earth Object Observations (NEOO) is sponsoring several studies of techniques for impact mitigation.
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.
Impact effects studies are ongoing at some of the Department of Energy’s national laboratories.
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.”
NEOShield is considering kinetic impactor options, blast deflection techniques, and gravity-tractor methods.

34. How Do We Mitigate the Hazard of Possible Asteroid Impacts?
Consider our options once a hazard is detected:
Use nuclear explosion?
Small pieces could rain down on Earth
Radioactivity
Nudge it out of Earth’s orbit?
More likely to work technologically
Requires coordination on the global scale
Evacuate?
Need to know exact impact site
Might be impossible depending on the area
Note: no personal preparation plan is possible.

35. Asteroid mining

36. Asteroid mining: feasibility
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 -> more research is needed.
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
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

37. 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

38. 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.