Big Impacts

Impact Physics

  • Impact Earth is the topic.

Size and Frequency of Impacts

  • A graph shows the relationship between average time between Earth impacts (years) and object size (meters).

  • Examples:

    • 10 km object: impacts every 100 million years (catastrophic events).

    • 100 m object: impacts every 10,000 years.

    • 1 m object: impacts every year.

    • 1 mm object: impacts every 30 seconds.

    • 1 μm object: impacts every 30 microseconds.

Impact Velocity

  • An object falling to Earth from a large distance will hit the surface with a minimum velocity of 11.2 km/s (25,000 mph).

  • Planets mentioned: Venus, Mercury, Mars, Earth.

  • Near Earth Objects (NEO) are also mentioned.

Fireballs

  • Fireballs reported by US Government Sensors (1988-Apr-15 to 2025-Mar-27).

  • A graph displays Impact Energy vs log(kt).

  • Source: https://cneos.jpl.nasa.gov/fireballs/

  • Alan B. Chamberlin (JPL/Caltech) is credited.

Impact Velocity Distribution

  • Graph: Number Hitting Earth (1988 - 2023) vs. Impact Velocity [km/s].

  • Escape Velocity (VescV_{esc}) is marked on the graph.

Impact Scenarios

  • The Set Up:

    • Rock

    • Velocity (VV) = 11.2 km/s

    • Diameter = 10 km

    • Angle = 45°

Asteroid Orbits; Impact Velocity

  • Scenario 1:

    • _d = 1 AU

  • Scenario 2:

    • _d = 3 AU

    • Semi-major axis (aa) = 3 AU (asteroid orbit), radius (rr) = 1 AU (Earth's orbit).

    • Impact Velocity (VimpactV_{impact}) = 14.1 km/s.

  • Scenario 3:

    • _d = 30 AU

  • Scenario 4:

    • Semi-major axis (aa) = ∞ AU, radius (rr) = 1 AU (Earth's orbit).

    • Impact Velocity (VimpactV_{impact}) = 16.4 km/s.

Prograde vs. Retrograde Orbits

  • Prograde Orbits

  • Retrograde Orbits

  • Semi-major axis (aa) = 3 AU (asteroid orbit), radius (rr) = 1 AU (Earth’s orbit). Retrograde Orbits

    • Impact Velocity (VimpactV_{impact}) = 69 km/s.

  • Unbound Orbits

Interstellar Object

  • Oumuamua (1I/2017 U1) is the first known interstellar object to pass through the Solar System, estimated to be about 230 by 35 meters in size.

Tunguska Event

  • Occurred on the morning of June 30, 1908.

  • Explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 square kilometers (770 square miles) of forest.

  • Largest impact event on Earth in recorded history.

  • Image showing: LIMIT OF BLAST, TREE DAMAGE, EXPLOSION EPICENTER.

Impact Examples and Effects

  • Projectile = 75 m, Rate: 2,700 years

  • Boeing 747 Intercontinental is used for size comparison.

  • Various impact scenarios with a 75 m object are presented with different impact velocities, resulting in different wind speeds and damage areas:

    • D = 75 m (11.2 km/s) [NEO]

    • D = 75 m (16.4 km/s) [Prograde Asteroid] – 800 KM/H WIND

    • D = 75 m (73 km/s) [Retrograde Asteroid] – 1,500 KM/H WIND

  • Wind speeds EFS WIND (320KM/H+) and EF3 WIND (220KM/H+) are mentioned.

  • Effects include trees knocked down.

Global Effects

  • A graph shows the relationship between average time between Earth impacts (years) and object size (meters).

    • 10 km object: impacts every 100 million years (catastrophic events).

    • 100 m object: impacts every 10,000 years.

    • 1 m object: impacts every year.

    • 1 mm object: impacts every 30 seconds.

    • 1 μm object: impacts every 30 microseconds.

Cretaceous-Tertiary Extinction

  • Science article from June 6, 1980, discusses the extraterrestrial cause for the Cretaceous-Tertiary extinction.

  • Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock.

  • Dust would stay in the stratosphere for several years, suppressing photosynthesis and causing extinctions.

  • Asteroid diameter estimated to be in the range of 10 ± 4 kilometers.

  • Dinosaurs and space are conceptually linked.

Phanerozoic Climate Change

  • A graph shows Phanerozoic Climate Change over millions of years ago.

  • Glacial Periods are indicated.

  • Climate zones: Tropical, Arid, Cool Temperate and Warm Temperate.

Marine Biodiversity

  • A graph shows marine biodiversity over millions of years ago.

  • Number of genera are displayed over time.

Iridium Anomaly

  • Iridium anomaly is discussed as evidence.

  • Iridium concentrations measured in parts per billion (ppb).

  • Anomalies are shown at the K-T impact layer.

Earth vs Asteroid

  • Earth shown to be bigger than asteroid, Asteroid bigger than Earth

  • log10(earth/asteroid)

Iridium Abundance

  • Earth's Crust: 0.3 - 0.4 ppb

  • Ordinary Chondrite Meteorites: 500 - 750 ppb

Meteorite Classification

  • Stony: 94.6%

  • Stony Iron: 1.0%

  • Iron: 4.4%

  • Chondrites: 86.2%

  • Achondrites: 8.2%

  • Most common type of material to hit Earth.

  • Shon

Impact Signatures

  • Shocked Quartz

  • A graph shows the relationship between Max Size of Shocked Quartz and Palaeodistance.

  • Tektites

  • Glass Spherules

K-T Boundary

  • K-T Boundary analysis in Haiti.

  • Sample ages around 65 million years.

Impact Event Dynamics

  • Shock Wave diagram.

  • Crater?

Tsunami Deposits

  • A Tsunami Deposit at the Cretaceous-Tertiary Boundary in Texas is mentioned with reference to a Science article from 1988.

  • The most likely source for such a tsunami at the Cretaceous-Tertiary boundary is a bolide-water impact.

Chicxulub Crater

  • Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico.

  • Discussed in a Geology report from September 1991.

  • Impact Breccia: Rock composed of broken fragments of minerals, rocks, or even other pieces of breccia.

  • Impactor size

  • Blast Radius

The Ends of the World

  • Referenced book by Peter Brannen describing the Chicxulub impact event.

  • The asteroid punched a hole of outer space vacuum in the atmosphere, expelling earth into orbit within a second.

Ignition of Vegetation

  • Global maps showing the locations where the power radiated to the ground is sufficient (12.5 kW/m² for >20 min) to ignite vegetation.

Soot and Iridium

  • Boundary Clay, Woodside Creek, New Zealand

  • York Canyon Core, Raton Basin

  • Graphs show the relationship between relative depth and Ir (ppt) with Fern Spores/ Angiosperm Pollen.

Impact Effects Timeline

  • Kring (2000) Model: Immediate, Months, Years, Decades

  • Fires, Dust Loading, Fireball radiation, Airblast, Earthquakes, Tsunamis, Burial beneath ejecta, Burning, Soot cooling, Pyrotoxins, Acid rain, No photosynthesis, Loss of vision, Cooling

  • Temperature change due to reentering ejecta, dust loading, soot, NO<em>xNO<em>x, H</em>2OH</em>2O and CO<em>2CO<em>2 greenhouse warming, and SO</em>2SO</em>2.

Mass Extinction at the Cretaceous-Paleogene Boundary

  • Science article discussing the Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary.

  • The Chicxulub impact triggered the mass extinction through environmental perturbations like darkness and cooling.

  • Release of Climate-Active Gases by Large Meteorite Impacts with a Case Study of Chicxulub.

  • Estimated release of 325 ± 130 Gt of sulfur and 425 ± 160 Gt CO2CO_2 into the atmosphere.

  • The New York Times article on Huge Asteroid impact as Central Villain in Dinosaurs' Extinction.

  • Temporal niche expansion in mammals from a nocturnal ancestor after dinosaur extinction.

End Permian Extinction

  • Araguainha crater: Diameter: 40 km(25 mi), Age: 254.7 Myrs

  • The catastrophe that killed off the majority of life on Earth 250 million years ago was not a meteorite impact, but a gradual rise in global temperatures.

Cataclysmic Asteroid Size

  • A chart showing the size range from 1 CM to 10,000 KM with the effects of impact.