Piedras Del Cielo

Piedras del Cielo

Alejandro García Universidad de los Andes Bogotá, Colombia

Charla Pública, AdeLA 2014 Planetario de Santiago, Chile, 30 de septiembre de 2014 ADeLA2014 Astronomía Dinámica en Latino-América

Colombia

Bogotá z BOG-SCL 4247 km Colombia

Bogotá

8'000.000 hab. Departamento de Física

Grupo de Astronomía

http://fisica.uniandes.edu.co Motivación

Distribución de Impactos en la Tierra

KNOWN IMPACTS ON THE EARTH METEOR CRATER ARIZONA Classic meteorite crater, 1 km wide, 185 m deep.

Known to to be a meteorite crater for the following reasons: 1 Steep sides and closed, 2 Rim uplifted and tilted away from center 3 inverted piles of rock found outside the crater, 4 large blocks of limestone found outside crater, 5 Crater has 265 m of shattered rock, 6 Numerous pieces of nickel-iron found in the area and 7 High P/T rocks including fused sandstone and shatter cones. 30 m diameter meteorite about 50,000 years ago. KNOWN IMPACTS ON EARTH THE CRETACEOUS/TERTIARY BOUNDARY EVENT Chicxulub structure

Around world at K/T boundary found large amounts of Iridium. Rare on Earth. Common in meteorites. Suggested meteoritic collision with the Earth. Evidence suggested came down in the Caribbean. Circular gravity anomaly off the tip of the Yucatan Peninsula. PMEX had drilled exploratory holes in the area which had encountered shattered rock and glasses

Geophysical surveys shoed circular structures at depth. Seismic data showed an inner and outer ring of 80 and 195 km diameter. Gravity and magnetic structures show some opening to the North west. Suggests a 10 km asteroid slammed into the Earth at a 20 - 30 degree angle 64.98 Ma

ENVIRONMNETAL EFFECTS IMPACTS CRATER FORMING PROCESS Comet or Asteroid hitting the Earth

Large meteorites form complex craters 1 incoming meteoroid hits earth at speeds as high as 30km/sec 2 Impact shock creates high P & T that vaporizes most of the crater rock and the meteoroid

ENVIRONMENTAL EFFECTS IMPACTS CRATER FORMING PROCESS Comet or Asteroid hitting the Earth

1 The release wave following the shock wave causes the center to rise.

1 The fractured walls slide into the crater producing wider and shallower rim.

Outer walls can have a diameter 100 times the depth.

ENVIRONMENTAL EFFECTS IMPACTS PROBLEMS FOR LIFE FROM IMPACTS

Impact of K/T asteroid had major effects on surface temperature. First, a fireball and hot gases that lasted many hours. Second, temperatures dropped to winter conditions as dust and ash blocked out sunlight. Third, o after dust settled C0 2 remains aloft creating greenhouse warming of 10 C. Also have major 300 m tsunami and a huge steam bubble. EVENTS OF THE TWENTIETH CENTURY COMET EXPLOSION Tunguska, Siberia 30 June 1908

Strange event in unpopulated Siberia. Massive fireball exploded 8 km above ground.

Produced very bright light in northern Europe.

Found all the trees in a 30 x 30 km area knocked down.

No impact crater or even broken ground. 30 to 50 m meteorite exploded above ground.

Expedition in 1958 found evidence of melted iron and silica rich rock.

If over Washington do tremendous damage.

30 de junio de 1908

1921 EXPEDICIÓN

Distribución de Impactos en la Tierra

574 REGISTROS EN CHILE

EVENTS OF THE TWENTIETH CENTURY BIGGEST NEAR EVENTS Meteor/Asteroid diameter, crater size and life

Beyond 100 m diameter meteoroids have a devastating effect on life EVENTS OF 20TH Escala de Torino CENTURY BIGGEST NEAR EVENTS Assessing Hazards

Have Torino scale which assesses hazards on a 0 - 10 scale.

Enables calm communication about the threats.

FREQUENCY OF LARGE IMPACTS

Over 2000 NEO’s. 25-50% will eventually hit the earth. Average time between impacts is 100,000 years. Risk being killed by impact is 1 in 20,000. High because a huge number of people 1.5 Billion will be killed in an impact. ANNUAL RISK OF DEATH

Asteroids

● All planets and moons have been modified chemically and geologically. ● Where do you look for a piece of the original “stuff” of the solar system? ● Asteroids and comets. ● Small objects – Little internal heat, little to no geological activity. – Little gravity, little to no atmosphere.

Orbits 1. Asteroid belt. 2. Same as Jupiter, but separated by 60º - Trojans 3. Elliptical orbits that pass Earth • Earth-crossing asteroids: – Near-earth asteroids (NEAs) – Near-earth objects (NEOs)

Asteroid sizes

● How big are they? – Largest (Ceres) is 940 km in diameter – Three larger than 500 km – About a dozen larger than 250 km – Number increases rapidly with decreasing size ● Total volume of all asteroids ~ much smaller than moon.

Asteroid Encounters

● fly-bys of asteroids: – Gaspra by Galileo in 1991 – Ida by Galileo in 1993 – Mathilde by NEAR in 1999 ● orbiters: – Eros by NEAR in 2000 – Itokawa by Hayabusa in 2005

Eros

Itokawa

Density

● Calculate Density ● Rock ( ~ 3g/cm3) vs. metal (~7g/cm3). ● Solid vs. rubble pile. ● Ida = 2.6 g/cm3 ● Eros = 2.4 g/cm3 ● Itokawa = 1.9 g/cm3 ● Mathilde = 1.5 g/cm3 ● Eugenia = 1.12 g/cm3

Meteorites

Primitive

Processed: stony-iron

Processed: iron Peekskill Meteorite oct 1992

Peekskill Meteorite oct 1992 $125 por gramo

Forming Doublets

● Random impacts (unavoidable) ● Very oblique impacts, ricochet (Messier, Messier A) ● Endogenic crater formation (volcanoes, collapse pits, etc.) ● Atmospheric break-up, explosion (Henbury) ● Tidal break-up (Shoemaker-Levy 9) ● Spatially clustered secondaries ● Impact of binary asteroid or comet

Physical Properties of Decameter-scale Asteroids

http://www.oosa.unvienna.org/oosa/e n/COPUOS/stsc/wgneo/index.html Systems Engineering Approach to the Mitigation of Hazardous Near- Earth Objects (NEOs)

Brent William Barbee, M.S.E. Emergent Space Technologies, Inc. July 11th, 2006

NEO Deflection Methods

● Deflection is the preferred mode of mitigation. – Most practical mitigation mode, given current and foreseeable technology. • Energy requirements are tractable for a wide range of NEOs. – Most controllable, generally. • With practice we can develop proficiency and learn the pitfalls. – This is absolutely critical if we are to be prepared.

NEO Deflection Methods

● Deflection has its difficulties: – Rubble piles or highly porous NEOs. – Some proposed deflection systems are very challenging to implement due to: • Anchoring to NEO surface. • Complex proximity operations about NEO. • NEO spin state. • Long periods of operation on orbit in hostile space environment. – Higher probabilities of failure. – All proposed systems are currently untested.

NEO Deflection Methods

● Some possible deflection systems: – Gradual • Solar concentrators • Attached low-thrust thrusters • Gravity tractor – Impulsive • Kinetic impactors • Attached high-thrust thrusters • Nuclear explosives – Standoff blast – Surface blast

NEO Deflection Methods

● Nuclear explosives offer the following advantages: – NEO spin state not a factor. – No anchoring of equipment to NEO. – No long operation on orbit. – Highest available energy density. • High capability for imparting momentum to a NEO. – High energy density equates to easier launch from Earth. • Multiple launches are more feasible.

NEO Deflection Methods

– High momentum transfer performance: • Can adequately deflect larger NEOs than other methods even with limited warning time. – Technology is currently available. – Puts former weapons of mass destruction to a use that benefits all humankind. – Deflection is relatively controllable through proper positioning of the device prior to detonation.

NEO Deflection Methods

● Nuclear explosive disadvantages: – Untested. – Required rendezvous and proximity operations are challenging in some cases. – Requires special packaging inside launch vehicle to ensure containment in the event of launch vehicle failure. – Danger of inadvertently fragmenting NEO in an undesirable fashion.

NEO Deflection Methods

– Sensitive to NEO physical properties. • In the absence of good knowledge of NEO physical properties, the system must be over-designed. – Requires amendment of the “Nuclear Test Ban Treaty” (1963). – Public fear and misunderstanding. – Political tensions.

NEO Deflection Methods

● Standoff nuclear detonation: – Nuclear device of proper yield is placed at the optimal detonation coordinates. • Optimal distance from NEO surface. • Optimal orientation of imparted impulse vector. – Neutrons from the explosion penetrate 10-20 cm into NEO surface, superheating a thin shell of NEO material. – Material blows off and imparts momentum to NEO.

NEO Detection

● NEO discovery and cataloguing: – Detection and observations: • LINEAR • NEAT • LONEOS • Catalina Sky Survey • Spacewatch http://www.ll.mit.edu/LINEAR/ – Tracking and threat characterization: • Near-Earth Asteroid Tracking (NEAT) program at JPL • Near-Earth Objects Dynamic Site (NEODyS) in Pisa, Italy

NEO Detection Catalina Sky Survey

NEO Detection

NEO Threat Characterization

● Palermo Scale P P=log I - Palermo Scale Value 10 (P ΔT ) B

- Probability of Impact PI P - Annual Background Probability of Impact B for a NEO with Same Kinetic Energy

ΔT- Time in Years Before Impact

Tipos de Meteoritos

• Types – just like asteroids! – stony (incl. carbonaceous chondrites) – irons & iron / nickel (90% / 10%) – stony-irons (a combination of materials) – the type of meteorite tells you where it came from.

61 •Meteoritos rocosos (difíciles de encontrar)

62 •Meteoritos ferrosos (fáciles de encontrar)

63 •Meteoritos carbónicos

64 •Meteoritos ferro-rocoso-cristalinos

65 Los meteoroides se formaron en cuerpos mayores (planetesimales)

Rocosos se forman en el manto Ferrosos se forman en el núcleo

66 Los meteoroides provienen de la materia condensada más temprana en el sistema solar. Ellos nos dan la composición química de los primeros planetisimales.

La mayoría tienen una edad ~ 4.6 millones de años. 67 Cinturón de Asteroides

En general, a las afueras de la órbita de Marte, 2.7 a.u. distancia media.

La masa total de todos los asteroides es <5% de la masa de la Tierra.

68 4 69 5 Clases de Asteroides

• S – Rocoso (Stony)

• C – Carbonaceo (Carbonaceous) (asteroides rocosos con superficies oscuras y cavidades interiores) • M – Metálicos (Metallic) (poco frecuentes)

70 8 Asteroides Rocosos

Gaspra – a typical stony asteroid 71 9 Se piensa que algunos asteroides son Pilas de escombros que se mantienen unidas debido a su baja gravedad.

72 10 Vesta

P=5.3h

73 12 Asteroides mayores

• Vesta – más pequeño (R=250 km), pero mucho más brillante. Apenas visible a simple vista.

• Pallas • Juno

74 14 Toutatis - uno de los más cercanos!

Toutatis gira sobre 2 ejes.

De 5 km. Pasó tan sólo a 29 distancias lunares de la tierra en 2000. 75 19 Comet Shoemaker-Levy 9 broke into a series of fragments before impacting Jupiter. (1994)

The ‘fireball’ from each impact was larger than the earth.

76 39 An atmospheric “scar” left by the impact of Shoemaker-Levy 9. These faded after several weeks.

77 40 http://www2.jpl.nasa.gov/sl9/image81.html 79 46 80 47 Comet particles trapped in the aerogel (a light silicon gel).

81 50 Misión Rosetta

• Rosetta – launched 2004 to comet 67P/Churyumov-Gerasimenko. Rosetta will fly along with the comet for 2 years as it approaches the sun, beginning in 2014. It also has a small lander which will explore the comet’s nucleus.

• http://sci.esa.int/where_is_rosetta/

82 52 Asteroid observations

PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY ASTEROIDS # Observations of 1980 Tezcatlipoca at OHP

# Two nights: 25/07/2006 (63 frames), 30/07/2006 (55 frames) # Telescope: 1.20 cm # Detector: CCD TK1024 # Filter: R # Exposure time: 120 s

PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY ASTEROIDS # Selected reference stars and asteroid (1980 Tezcatlipoca)

LOWELL OBSERVATORY LONEOS Schmidt telescope

Detección NEO's

http://www2.jpl.nasa.gov/sl9/image81.html Detección NEO's

http://www2.jpl.nasa.gov/sl9/image81.html Detección

Detección/ Falsos +

Detección ESO/ PARANAL

Detección Gaia

Detección ALMA

Preguntas

http://www2.jpl.nasa.gov/sl9/image81.html