AST 301, Debris Lecture

James Lattimer

Department of Physics & Astronomy 449 ESS Bldg. Stony Brook University

February 26, 2019

James Lattimer AST 301, Debris Lecture Debris in the Solar System: Comets Hale-Bopp

I “Dirty snowballs”, a mixture of ices and dust, ejected from solar system when planets formed I Mass mostly contained in a nucleus (solid dirty snowball) with km-sized diameter Hally’s nucleus I Coma, a cloud of H2O, CO2 and other gases va- porized from nucleus during close passage to Sun from Giotto I Hydrogen cloud, huge but sparse neutral H cloud I Dust tail, 1–10 million km long, dust driven oﬀ nucleus by escaping gases when close to Sun I Ion tail, 100’s of millions of km long, plasma driven oﬀ by solar wind I Most comets reside far outside the orbit of Pluto, a few occasionally perturbed into close-solar orbits; some are in elliptical orbits and reappear I After a few hundred passages near the Sun, icy material is lost, Shoemaker-Levy 9 before Jupiter impact leaves dead comet which can be mis- taken for asteroid.

James Lattimer AST 301, Debris Lecture Comet Holmes, Halloween, 2007 V. Peris and J. L. Lamadrid

Fragment G HST 7/18/1994

Shoemaker-Levy 9 HST 7/7/1994

James Lattimer AST 301, Debris Lecture Comets History I Records of comets exist at least to 1140 BC I Brahe observed comet of 1577, proved they are extraterrestrial I Halley: some comets are periodic (1531, 1607, 1682)

I Halley’s Comet: 2467 BC (?), 240 BC (China), 1066 (Bayeux Tapestry)

I Motivated Newton to develop gravity theory Orbits I Hyperbolic: pass Sun once, depart forever I Elliptical: periodic I Peri-/Aphelion: closest/farthest solar approach Origin I Short-period come from Kuiper Belt, 35,000 icy bodies larger than 100 km, 30-100 AU I Long-period come from Oort comet cloud, ∼ 1012 comets, 30,000 AU–1 lt. yr. I Most formed within inner solar system, then pushed outwards by repeated near encounters James Lattimer AST 301, Debris Lecture Giotto’s Adoration of the Magi

From 1301 appearance

James Lattimer AST 301, Debris Lecture Missions to Comets

I International Cometary Explorer (ICE), August 1978, Comet Giacobini-Zinner (Sept. 1985), Comet Halley (Mar. 1986)

I Vega-1 and Vega-2, December 1984, left landers on Venus, Comet Halley (Mar. 1986)

I Sakigake and Suisei, January 1985, Comet Halley (Mar. 1986)

I Giotto, July 1985, Comet Halley (Mar. 1986), Comet Grigg-Skjellerup (Jul. 1992)

I Deep Space 1, October 1998, asteroid 9969 Braille (Jul. 1999), Comet Borrelly (Sep. 2001)

I Stardust, February 1999, Comet Wild 2 (Jan. 2004, returned dust particles to Earth in 2006), Comet Tempel (2011)

I Contour, July 2002, lost.

I Deep Impact, January 2005, Comet Tempel 1 (also impactor), Comet Hartley 2 (Nov. 2010), Comet Garradd (Feb.-Apr. 2012), Comet ISON (Jan. 2013)

I Rosetta, March 2004, asteroids 2867 Steins (2008) and 21 Lutetia (2010), Comet 67P/Churyumov-Gerasimenko (Aug. 2014)

James Lattimer AST 301, Debris Lecture Halley’s Comet and Giotto

Size is 15 × 8 × 8 km. Density is very small, 0.3 g cm−3. Water, CO and CO2 were 80%, 10% and 2.5% of matter ejected. Traces of hydrocarbons, iron, sodium observed. Abundances of light elements (except N) are same as in Sun. Albedo blacker than coal. Jets threw out 3 tons/s.

James Lattimer AST 301, Debris Lecture Comet Shoemaker-Levy 9

I This comet was discovered by Eugene and Carolyn Shoemaker and David Levy on March 18, 1993. I The comet may have been captured by Jupiter in 1966. I The comet apparently broke apart due to tidal forces on July 7, 1992 on a close approach 25,000 to 120,000 km away. I The comet’s original size was about 1.5 to 2 km in diameter. I The comet fragments crashed into Jupiter from 16 to 22 July, 1994. I The total released energy was about 300 Gtons of TNT. I Plumes rose to 3000 km height, and the atmosphere near the impacts was heated to 40,000 K. I Other objects have been seen to impact Jupiter in 2009, 2010 (twice), 2016 and 2017. I The SL-9 homepage was the ﬁrst major global webpage on www. I The SL-9 impact likely was the trigger for NASA to receive funding for NEO searches. I Comet Schwassmann-Wachmann 3 was observed to brighten in September 1996 and split into 8 or more pieces between October and December 1996.

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture Deep Space 1

I Designed to test a dozen new technologies including an ion engine.

I Launched in October 1998, it completed testing the technologies in less than a year.

I Made a bonus ﬂyby of 9969 Braille in July 1999, approaching within 17 miles.

I While making a new journey to comet Borrelly, star tracker orientation system failed in November 1999. Comet Borrelly I By June 2000, engineers were able to use the on-board camera as a replacement navigational tool. Probably the most successful robotic space rescues in history.

I Approached comet Borrelly in September 2001, took best comet pictures up to that time.

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture Stardust

I Designed to study comet Wild 2, a comet Annefrank perturbed by Jupiter from a long-period to short-period comet in 1974, in 2004.

I Designed to capture comet and interstellar dust with an aerogel collector, and return dust to Earth. Comet Wild 2 I Flyby of asteroid 5535 Annefrank (Nov. 2002) and comet Wild 2 (Sep. 2004), Earth sample return (Jan. 2006), and ﬂyby of comet Tempel 1 (Feb. 2011).

I Evidence found for liquid water and the amino acid glycine in comet Wild 2.

I Results showed outer regions of solar system were not isolated and were not a refuge of interstellar matter, and matter from the high-temperature inner solar system was mixed into the Kuiper Belt.

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture Comet Tempel 1 and Deep Impact Mission

I Discovered April 3, 1867 by Ernst Wilhelm Leberecht Tempel of Marseilles, France.

I Recognized as periodic by Bruhns of Leipzig; P = 5.68 years.

I In 1881, the comet had a close encounter with Jupiter and its period changed to 6.5 years, and perihelion was increased from 1.8 AU to 2.1 AU.

I The comet was subsequently lost, due to close approaches with Jupiter in 1941 and 1953, among others.

I Presently, comet is in a 1:2 resonance with Jupiter, P = 5.5 years. James Lattimer AST 301, Debris Lecture Tempel 1 and Deep Impact

NASA

James Lattimer AST 301, Debris Lecture Tempel 1 and Deep Impact

NASA

James Lattimer AST 301, Debris Lecture Tempel 1 and Deep Impact

T - 3 min. T + 12 min. T + 1 hr. 4 min.

HST

T + 1 hr. 28 min. T + 4 hr. 41 min. T + 19 hr. 7 min.

Comet 9P/Tempel 1 • July 4-5, 2005 Hubble Space Telescope • Advanced Camera for Surveys

NASA, ESA, P. Feldman (Johns Hopkins University) and H. Weaver (Johns Hopkins University Applied Physics Laboratory) STScI-PRC05-17c

James Lattimer AST 301, Debris Lecture Comet Tempel 1 Impact Site

James Lattimer AST 301, Debris Lecture Comet Tempel 1

Deep Impact

Recession due to sublimation.

Stardust

James Lattimer AST 301, Debris Lecture Tempel 1 Findings

I It’s a ﬂuﬀ ball, about 50/50 rock and water ice grains. I Rock dust consists of silicate grains, like crushed gems, smaller than sand grains. I Clays and carbonates also exist (seashells made from these), which is unexpected because it is thought they need liquid water to form. I This may indicate a more thorough mixing of primordial solar system matter, so that grains formed in liquid water near the Sun are mixed with icy material from out by Uranus and Neptune.

water iceH 2O dry iceCO 2 olivine (Mg,Fe)Si2O4 montmorillonite clay (Al, Si, O) polycyclic aromatic hydrocarbons

spinel MgAl2O4 iron Fe

enstatite MgSiO3 dolomite CaMg(CO3)2 marcasite FeS2

SPACE.com

James Lattimer AST 301, Debris Lecture Findings Concerning Comet Hartley-2

I A pebbly trail discovered by WISE = Wide-ﬁeld Infrared Survey Explorer

I Deep Impact found its core does not have a uniform composition: jets

spewing ice and CO2 in one direction, and others spewing water vapor but

no CO2. I Deep Impact also found three types of ices: H2O with methanol,

CO2, and C2H2 (ethane).

James Lattimer AST 301, Debris Lecture Comet 67P/Churyumov-Gerasimenko Discovered September 1969 Deﬂected by Jupiter in 1840 and 1959 Perihelion moved from 4AU to 1.3AU Orbital period is 6.45 yr. Size is 4.3 × 2.5 × 4.1 km Mass is 1016 g

Comet 67P/Churyumov-Gerasimenko

Albedo is blacker than coal Density is less than water

James Lattimer AST 301, Debris Lecture Rosetta

James Lattimer AST 301, Debris Lecture Philae

James Lattimer AST 301, Debris Lecture Rosetta

James Lattimer AST 301, Debris Lecture Gases Detected: Comet 67P/Churyumov-Gerasimenko

Water, carbon monoxide, carbon dioxide, ammonia, methane, ethane, propane, butane, pentane, hexane, heptane, formic acid, acetic acid, acetaldehyde, ethylenglycol, propylenglycol, butanamide, methanol, ethanol, propanol, butanol, pentanol, glycine, argon, krypton, xenon, cyanogen, acetylene, hydrogen cyanide, acetonitril, formaldehyde, sodium, potassium, silicon, magnesium, hydrogensulphide, carbonylsulphide, sulphur monoxide, sulphur dioxide, carbon disulphide, nitrogen, oxygen, hydrogenperoxy, benzene, toluene, xylene, benzoic acid, naphthalene, hydrogen ﬂuoride, hydrogen chloride, hydrogen bromide, phosphorus, chloromethane, methylamine, ethylamine, sulphur, disulphur, trisulphur, tetrasulfur, methanethiole (CH3SH), ethanethiol (C2H5SH), thioformaldehyde (CH2S)

James Lattimer AST 301, Debris Lecture Asteroids

I Also called minor planets or planetoids, largely lying within the orbits of Mars and Jupiter (main asteroid belt). I Objects lying outside Neptune are called trans-Neptunian objects, centaurs or Kuiper-Belt objects. I The first asteroid to be discovered was Ceres on Jan 1, 1801. I Total asteroid mass is about 4% of the Moon’s mass. Ceres is about 32% of this. The first 4 asteroids have 51% of the total. I Can be roughly classified by spectral type: C-type carbonaceous, 75% S-type silicaceous, 17% L-type metallic, 8% These percentages do not reflect true proportions, but only observed proportions; some are easier to see than others. I About a third of asteroids are members of families that have similar orbits. Probably they form as a result of collisions between asteroids. They last for about a billion years. I Asteroids are slowly lost due to collisions with planets and to gravitational encounters that eject them from solar system. I Trojan asteroids collect in Lagrangian points (stable gravitational minima) 60◦ ahead of and behind Jupiter in its orbit. Similarly for Mars, Earth and Venus. I Asteroids are given a number in order of their discovery and the discoverer or the IAU may name them. James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture 951 Gaspra

243 Ida

433 Eros

James Lattimer AST 301, Debris Lecture Heat Sources

I Collisions and accretion

I Radioactivity

I Tides

I Exothermic chemical processes

I Electrical currents from intense early solar wind

I Lightning

I Friction

I Gravitational potential energy In a solid object, the ﬁrst heat source of importance is from accretion, but this is unlikely to have entirely melted bodies. Collisions could melt surface layers. In a large enough object, radioactivity could melt entire bodies.

James Lattimer AST 301, Debris Lecture Major Radioactivities

Nucleus Decay Product Half Life Sm147 Nd143 106 Gyr Rb87 Sr87 48.8 Gyr Th232 Pb208 14.4 Gyr U238 Pb206 4.47 Gyr K40 Ar40 1.25 Gyr U235 Pb207 0.70 Gyr I129 Xe129 15.7 Myr Al26 Mg26 717,000 yr Cl36 Ar36 301,000 yr Kr81 Br81 210,000 yr C14 N14 5730 yr H3 (tritium) He3 12.43 yr

James Lattimer AST 301, Debris Lecture Example

• Sample contains three minerals A, B, C. • Minerals have different chemical abundances and different Rb/Sr ratios. Sr87 and Sr86 are stable, Rb87 is radioactive. • When the rock solidified, the isotopic ratios of each mineral had equal values of Sr87/Sr86 as per line “Then” • For each decay of Rb87, a Sr87 nucleus is produced, so the points move in a 45◦ northwesterly direction as time proceeds. • Today, the isotopic ratios of each mineral lie on line “Now”. • The older the sample, the larger the angle θ becomes: tan θ = t/t1/2 • The angle θ is 45◦ after 1 half life when t = t1/2.

James Lattimer AST 301, Debris Lecture Radioactivity in our Lives Radioactivity in nature has three components: Primordial from before the creation of the Earth Cosmogenic produced by cosmic rays Artificial due to human activity Source Dose (USGS) mrem/yr Inhaled (Mostly Radon 200 Other ingested 39 Terrestrial radiation 28 Cosmic radiation 27 Cosmogenic 1 Artificial (medical) 50 Artificial (consumer products) 9 Artificial (coal + nuclear) 1 Total 355 A rem measures the equivalent dose and is equal to the absorption of 100 erg per g of material times a quality factor that depends on the radiation. At an altitude of 1 mile, add 27 mrem to total, on the Colorado Plateau, add 63 mrem to total, add 1 mrem for each 1000 miles traveled by jet. Add 7 mrem if you live in a stone, brick or concrete building and 1 mrem for too much TV.

James Lattimer AST 301, Debris Lecture Carbon Dating earthsci.org/fossils/geotime/radate/radate.html

• C14 originally on the Earth has long since decayed. • Cosmic rays bombard N nuclei in atmosphere at a steady rate, converting some of them to C14. • Rate of production by cosmic rays balances rate of decay, building up a steady-state abundance of C14 • Atmospheric abundances of C isotopes: C12 98.89%, C13 1.11% and C14 0.00000000010% • C12/C14 = 1 trillion:

This is the ratio found in (1949) Libby & Arnold living tissue • Dead tissue loses C14 by radioactive decay: −t/8266yr C14(t) = C14(0)e

James Lattimer AST 301, Debris Lecture Nuclear Hysteria and Irrational Fears

I Closing of nuclear accelerator at Brookhaven National Lab in 1997 due to small tritium leak – equivalent to amount used in exit signs. • Loss of medical research accelerator use and user fees • Clean-up cost was millions of dollars • Tritium radiation levels were lower than federal standards (4 mrem/yr), would have decayed before reaching groundwater. • Even if drunk, tritium is rapidly evacuated from the body on timescales much less than decay times. • Clean-up was forced by political pressure from several environmental and anti-lab groups. I Continued reliance on coal (56%) rather than nuclear (18%) power CO2 emission: Coal 2 billion tons/year, same as 300 million autos. Nuclear: 0. Pollution: Coal burning releases 64% SO2, 26% nitrous oxides (contribute to ozone loss), 33% mercury, plus arsenic, cadmium, chlorine, lead, titanium, etc. Radiation: Coal burning eﬀectively emits about 100 times more radioactivity (as particulate U, Th, K, etc., in exhaust) than nuclear, per unit of power generated. Health Costs: Multiplies cost of coal by 3 - 4 times; adds $500B (Harvard). James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture Evidence for Radioactivities in the Early Solar System

I There is a tight correlation in mineral grains from the Allende meteorite between abundances of Al with the decay product of 26Al, 26Mg.

I Because the halﬂife of 26Al is only 700,000 yrs., it had to be produced just prior to the collapse leading to the formation of the solar system. 26 I Thus, Al was present when meteorites formed and could be the signature of a nearby supernova. James Lattimer AST 301, Debris Lecture Al26 in the Galaxy

26 I The amount of Al implies a gravitational collapse supernova rate of about 2 per century in the Galaxy. Most must occur in inner galaxy and remain invisible to us, obscured by dust and gas.

26Al

Max Planck Institute, Garching

James Lattimer AST 301, Debris Lecture Al26 in the Galaxy as a Probe of Rotation

I Traces galactic rotation through Doppler shifts.

Max Planck Institute, Garching

James Lattimer AST 301, Debris Lecture Radioactive Heating

I is the energy released per radioactive decay. I τ is the mean lifetime of a radioactive nucleus. I Y is the initial fraction of all atoms that are radioactive. I N is the total number of atoms in an asteroid. I M is the total mass of an asteroid, ρ is the density. 4π µ M = ρR3 = N 3 No

I µ is mean molecular weight; total internal energy is E = 3NkB T /2. −t/τ I The heating rate of an asteroid is NY (/τ)e . 2 4 I The cooling rate of an asteroid is 4πR σT . dE 3 dT = Nk = NY e−t/τ − 4πR2σT 4. dt 2 B dt τ 26 I The maximum temperature is reached when dT /dt = 0. For Al :

1/4 1/4 1/4 NY e−tmax /τ N Y ρR R T = ∼ o ∼ 1000 K. max 4πR2στ 3eµτσ km

James Lattimer AST 301, Debris Lecture Meteorite Types

There are about 1050 observed falls and about 31,000 ﬁnds.

I Stony meteorites

I Chondrites (85.7% of falls, 52% of ﬁnds) oldest, 4.55 Byrs old.

I Ordinary contain both volatile and oxidized elements, formed in inner belt, and are the most common type. I Carbonaceous contain more volatiles, formed in outer belt. I Enstatite contain more refractory elements, formed in the inner SS.

I Achondrites (7.1% of falls, 1% of ﬁnds) show evidence of igneous processes.

I HED group I SNC group (Martian) I Aubrites I Urelites I Eucrites (Vesta)

I Stony iron (1.5% of falls, 5% of ﬁnds)

I Pallasites

I Mesosiderites

I Iron (5.7% of falls, 42% of ﬁnds) formed in meteorite parent body cores.

James Lattimer AST 301, Debris Lecture Meteorite Properties

I primitive: unaltered (mostly chondrites, esp. carbonaceous chondrites)

I diﬀerentiated: altered, products of melting, separation Interesting discoveries:

I Organic compounds in carbonaceous chondrites (Allende, Murchison) are equally left- and right-handed 16,17,18 26 I Isotopic anomalies in carbonaceous chondrites: O, Mg (from 26Al, halﬂife 720,000 yrs)

I SNC meteorites traced to Mars

I Possible microfossils, complex hydrocabons, biominerals in SNC meteorite ALH 84001

I Eucrites traced to Vesta

I Sayh al Uhaymir 169 is a meteorite from the Moon

I The meteorite Kaiduri is possibly from Mars’ moon Phobos

James Lattimer AST 301, Debris Lecture Meteorite Classiﬁcation

James Lattimer AST 301, Debris Lecture Asteroid-Meteorite Links 21 36 I Cosmic ray-produced radioactive isotopes (Ne , Ar ) determine traversal time in space. Ages range from 30,000 to 70,000,000 yrs. Not interstellar. I Solar wind (H, He, Ne, Xe) blasts meteorites. Abundances of these gases consistent with mean distances from Sun of 3 AU. I Solar wind gases and solar ﬂare particle tracks indicate exposure at surface of an airless body. I Many meteorites are made of broken fragments, remnants of projectiles of relatively low velocity. High proporition of broken fragments consistent with dense cratering seen on Ida, Gaspra, Mathilde and Eros. I Gravitational perturbations by Jupiter are thought to cause orbit changes from asteroid belt to Earth-crossing. About 900 asteroids larger than 1 km in Earth-crossing orbits at present; about 7% will eventually hit Earth. I Cooling rates of meteorites estimated to be between 1-100 C per million years, from size and composition of metal grains and Pu ﬁssion tracks in phosphate grains. This implies origination from centers of objects 100-300 km in diameter (i.e., a large asteroid). I 4.5 Gyr age of most meteorites indicate origination from small bodies, 100 km or less. Larger objects take too long to cool. I Similarity in spectral characteristics of meteoritic and astroidal materials. I 6 chondrite falls were photographed, allowing orbits to be reconstructed. They indicate orbits to Earth-crossing asteroids.

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture Heating History of Meteorites

I About 8% of chondrites (type -3) have not been hotter than 400-600 C. Agglomerations of pristine solar nebular material, including extrasolar grains from other stars.

I Type -4 to -6 chondrites had prolonged periods from 600-950 C, equilibrating minerals and recrystallized. Loss of some volatiles.

I Other meteorites, including iron and stony-iron, were melted completely, forming two immiscible liquids: low-density silicate melt and a high-density metal-sulﬁde melt. The silicate melt cools into igneous rocks known as achondrites, containing basalts. he metal-rich melts form iron meteorites.

I Stony irons form two groups: pallasites from the boundary of the metal core and the silicate mantle; mesosiderites from the basaltic surface of one body mixed with the metallic core material of another (perhaps the low-velocity collision between a metallic projectile with the basaltic crust of a diﬀerentiated body). 26 I Radioactive heating, primarily from Al seems to be the dominant mechanism; collisional heating is insuﬃcient given the relatively low impact velocities.

James Lattimer AST 301, Debris Lecture What is a Kuiper-Belt Object? The Kuiper Belt is a disk- shaped region past the orbit of Neptune extending roughly from 30 to 50 AU from the Sun containing many small icy bodies. It is now consid- ered to be the source of the short-period comets. About 1000 are known, and many (like Pluto) are in solarviews.com a 3:2 orbital resonance with Neptune.

Centaur objects, of which 9 are known, orbit between Jupiter and Neptune. Their orbits are unstable, and are probably displaced from the Kuiper Belt.

James Lattimer AST 301, Debris Lecture

solarviews.com Kuiper Belt Objects Name Diameter (km) 2003 UB313 2400 ± 100 Pluto 2320 2003 EL61 1200? 2005 FY9 1250? Charon 1270 Sedna < 1500? 2004 DW ∼ 1500 Quaoar 1200 ± 200 Ixion 1065 ± 165 2002 AW197 890 ± 120 Varuna 900 ± 140

solarviews.com

James Lattimer AST 301, Debris Lecture They Have Moons!

solarviews.com

James Lattimer AST 301, Debris Lecture What are Near-Earth Objects?

I Comets and asteroids deﬂected into orbits with perihelion distance q < 1.3 AU I Made of water ice plus embedded dust I Originated in cold outer solar system I Primordial, leftover building blocks of planets Classes of Near-Earth Asteroids: I Atens - Earth-crossing, semi-major axis a < 1.0 AU I Apollos - Earth-crossing, a > 1.0 AU I Amors - Earth-approaching but interior to Mars, a > 1.0 AU and 1 AU < q < 1.3 AU, NASA/JPL-Caltech I PHAs - Potentially Hazardous Asteroids I Closest approach to Earth less than 0.05 AU

I Absolute magnitude less than 22.0

I Assuming albedo is 13%, this means diameter greater than 150 m (500 ft)

I There are currently 1885 known PHAs, 157 are larger than 1 km

James Lattimer AST 301, Debris Lecture How Do We Find Near-Earth Objects?

I Early eﬀorts relied on comparison photographs taken several minutes apart

I Vast majority of objects recorded were stars and galaxies, which don’t move

I Special stereo viewing microscopes pick out NEOs

I Current eﬀorts use CCD cameras

I Computer-aided comparisons of digital images

I NASA’s goal: Find > 90% of NEAs > 1 km within 10 years I Total population estimated to be about 1000

I Lincon Near-Earth Asteroid Research (LINEAR)

I Near-Earth Asteroid Tracking (NEAT)

I Spacewatch

I Lowell Observatory Near-Earth Object Search (LONEOS)

I Catalina Sky Survey

I Japanese Spaceguard Association (JSGA)

I Asiago DLR Asteroid Survey (ADAS)

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture NASA Near Earth Object Program

James Lattimer AST 301, Debris Lecture 2018 GE3, a Recent Near-Miss 2018 GE3, April 14, 2018 Diameter: 48 - 110 m (3-6 times the size of Chelyabinsk meteor) Closest approach 192,300 km, velocity 106,500 km/h. Most of the rock would have disintegrated in the atmosphere. Between 2000 and 2014, there were 26 atomic-bomb-scale imacts in the Earth’s atmosphere detected in data from the Nuclear Test Ban Treaty Organization monitors.

James Lattimer AST 301, Debris Lecture Impacts Do Happen!

Comet Shoemaker-Levy 9, 1994

Peekskill, NY, 1992

James Lattimer AST 301, Debris Lecture NASA Near Earth Object Program

James Lattimer AST 301, Debris Lecture Tunguska, Siberia, 1908

James Lattimer AST 301, Debris Lecture Carancas, Peru, September 15, 2007

A chondritic meteorite hit near Carancas, Peru and poisioned about 30 villagers that approached the impact site (600 more had provoked psychosomatic ailments). The impact caused boiling of arsenic-contaminated ground water from natural deposits. The local province is turning this into a tourist attraction.

James Lattimer AST 301, Debris Lecture Chelyabinsk 2/15/2013 Diameter 20 m, velocity 19 km/s, altitude 30 km. 20-30 times energy of Hiroshima bomb, most powerful since Tunguska event. Many fragments recovered, largest was 654 kg.

James Lattimer AST 301, Debris Lecture Has No One Been Killed By A Meteorite?

10,700 BC End of Pleistocene: Great Lakes impacts linked to worldwide deposits of mammal bones and extinctions including wooly mammoths and saber-tooth tigers; disappearance of Clovis Culture 3123 BC Köfelsimpact event in Austria; impactor trajectory recorded on a Sumerian clay tablet 2807 BC Large impact in Indian Ocean caused megatsunamis 2200 BC Sudden fall of Sumerian civilization linked to impact 207 BC Bavarian impact of 0.7 mile diameter asteroid 536 BC Two impacts off Australia lead to megatsunamis and linked to reduced sunlight and crop failures in China and Mediterranean 580 AD Fireball near Bordeaux destroys Orleans 1348 AD Fireballs and earthquake in Carinthia kills 40,000 1430 AD Chinese fleet of Zhou Man destroyed, more than 173 ships, by comet 1490 AD Meteorite falls in Ch´ıng-yang, Shaanxi, China, killing more than 10,000 1631 AD 20,000 fatalities from a seige followed by a cataclysmic meteor impact in Magdeburg, Germany 1907 AD Family killed by meteorite in Hsin-pái,Weng-Li, China 2001 AD Red rain of Kerala, India, from comet disintegration

James Lattimer AST 301, Debris Lecture Impact Hazard

I Torino Scale: measures relative risks. Rating of 0 indicates no likely consequences; 1 object merits careful monitoring. I Palermo Scale: measures relative risk R.

PS = log10 R P R = Impact fB DT 4/5 fB = 0.03E is annual probability of an impact event with energy E in MT at least as large as the event in question. DT is the time until potential impact in years. I Top risks at present are

I 29075 (1950 DA) 2880-2880 with 1 potential impact, D = 1.3 km, PS=-1.42, TS=0

I 101955 Bennu (1999 RQ36) 2175-2199 with 78 potential impacts, D = 0.49 km, PS=-1.71, TS=0

I 41077 (2009 FD) 2185-2198 with 7 potential impacts, D = 0.16 km, PS=-1.78, TS=0

James Lattimer AST 301, Debris Lecture Studying Near-Earth Objects in Space Typical Instruments:

I Imager: Camcorder

I IR and UV spectrometers to infer mineralogical and gaseous compositions

I Lidar: Optical equivalent of radar, useful to deﬁne shape of target and aids in navigation

I X-ray, γ-ray and αX-ray spectrometers to infer chemical/elemental composition of surfae. X-rays come from Sun, γ-rays from cosmic rays, α-particles from a spacecraft Curium source

I Dust mass spectrometer detects high-velocity dust whose impacts produce ions

I Magnetometer to infer magnetic ﬁeld of target I Package to measure temperatures/densities of plasma clouds created as sun’s radiation ionizes cometary atmosphere. Also used to monitor DS1 spacecraft ion engine drive James Lattimer AST 301, Debris Lecture Spacecraft Missions

I Ice (8/12/1978 - 5/1985)

I 21P/Giacobini-Zinner I Giotto (7/2/85 - 7/10/92)

I Halley’s Comet 1985 and Comet 26P/GriggSkjellerup 1992 I Galileo (10/18/89 - 9/21/03)

I Flybys of 931 Gaspra and 243 Ida, discovered Dactyl I Near-Earth Asteroid Rendezvous (NEAR 2/17/96 - 2/12/01)

I Flyby of 243 Mathilde and 433 Eros, touchdown on 433 Eros I Deep Impact (11/1/99 - 7/4/05)

I Orbited and impacted on Comet Tempel 1, excavating a crater I Deep Space 1 (DS1) (10/25/98 - 9/22/01)

I Flybys of 9969 Braille and Comet Borrelly

I Tested new technology – ion drive rocket, concentrating solar panel, auto navigation system using asteroids I Stardust (2/7/99 - 1/15/06)

I 2 interstellar dust collections, ﬂyby of 5535 Annefrank, encounter with Comet Wild 2

I Discovery of olivine and other minerals containing Ca, Al and Ti, all hi-T condensates, in comet dust

James Lattimer AST 301, Debris Lecture More Spacecraft Missions

I Hayabusa (5/9/03 - 9/12/05) I landed on 25143 Itokawa (diameter = 600 m), planned sample return to Earth in summer 2007

I Suﬀered fuel leak after successful second landing, sample collected was only a few µg, returned it to Earth 2007. I Rosetta (3/2/04 - 2015) I ESA probe to Comet 67 Churyumov-Gerasimenko, utilizing 3 Earth and 1 Mars gravity assist mvrs.

I Orbited comet toward its perihelion for 17 months

I Included lander named Philae, island in River Nile containing obelisk with bilingual inscriptions providing Champollion with ﬁnal clues needed to decipher hieroglyphs of Rosetta Stone

I Flybys of 2867 Steins (5/9/08) and 21 Lutetia (7/10/2010) I New Horizons (1/19/06 - 1/1/19) I Pluto and moons 7/14/15

I 486958 (2014 MU69) 1/1/19 I Dawn (9/27/07 - present) I Vesta 7/16/11 - 9/5/12

I Ceres 2015 - present I Change’e-2 (1/10/10 - 13/12/12) I 4179 Toutatis

James Lattimer AST 301, Debris Lecture New Horizons at Pluto

James Lattimer AST 301, Debris Lecture Pluto and Charon

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture New Horizons at Ultima Thule

James Lattimer AST 301, Debris Lecture Change’e 2 at 4179 Toutatis

James Lattimer AST 301, Debris Lecture Dawn at Vesta

I A mountain in the south polar region 3 times higher than Mt. Everest.

I Equatorial troughs consistent with models of fractures due to giant impact.

I Diverse composition, particularly around craters.

James Lattimer AST 301, Debris Lecture Dawn at Vesta HST had suggested the entire south pole was one large impact crater, which suggested a way to deliver the HED meteortites (eucrites) thought to be Vesta material to Earth. Vesta is differentiated, separated by density into onion-like layers of different compositions, that would explain the different types of observed eucrites. This was confirmed by Dawn’s spectral observations. Dark spots and ejecta streaks were also observed. Believed to be hydrated material from elsewhere: carbonaceous chondrite matter plus water from debris originating farther out in solar system. James Lattimer AST 301, Debris Lecture Dawn at Ceres

James Lattimer AST 301, Debris Lecture Mineral Deposits

Probably brine or salty clay, sodium carbonate Na2CO3).

James Lattimer AST 301, Debris Lecture Eve More Missions

I Hayabusa 2 (12/3/14 - present)

I 162173 Ryugu, orbiterDCAM-3, landers MINERVA II-1 (Rovers-1A and B), MINERA II-2 and MASCOT, and impactor SCI

I SCI shot tantulum bullet into asteroid Feb. 25, 2019 and sample collected with a horn; may try for two more samples; will be returned to Earth Dec. 2020.

I OSIRIS-REx (9/8/16 - )

I 101955 Bennu, entered orbit Dec. 2018, touchdown and sample collection 2020, sample return Sep. 2023

I Lucy (planned for 2021)

I 52246 Donaldjohanson 4/20/2025

I 3548 Eurybates 8/12/2027

I 15094 Polymele 9/15/2027

I 11351 Leucus 4/18/2028

I 21900 Orus 11/11/2028

I 617 Patrocius 3/2/2033

I Psyche (planned for 2022)

I 16 Psyche 2026

James Lattimer AST 301, Debris Lecture Hayabusa 2 at 162173 Ryugu

James Lattimer AST 301, Debris Lecture James Lattimer AST 301, Debris Lecture Osiris Rex at Bennu

James Lattimer AST 301, Debris Lecture