Asteroids & Meteorites: The Hazards to Life

1. Asteroids & Meteorites: The Hazards to Life Ganna (Anya) Portyankina11 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.

3. Plan:

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).

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

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

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

8. 243 Ida and Dactyl

9. 433 Eros and 253 Mathilde

10. Bennu

11. 25143 Itokawa

12. 162173 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 • 162173 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 meteoritesconsist of almost equal parts iron-nickel metal and silicate minerals including precious and semi-precious gemstones. 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. There are two main types of stony meteorite: 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, 1992. 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 ThreatSize-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

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.