Astronomical impacts online student edition

1. Astronomical Impacts
Not Even!!!!!

2. High Rates of Speed Mean Really Big Impacts
Earth travels at an orbital speed of 108,000 km/h or 67,000 mph
Earth has a rotational speed of about 1,000 mph
Large asteroid travel at about 65,000 km/h or 40,000 mph

3. Wouldn’t Be
the First Time
Earth
Pummeled by space debris in its infancy
Responsible for our moon
Large asteroid hit Earth 4.5 bya
Debris coalesced and become out Moon
Impact scars rare on earth
Due to erosion and tectonic processes
Moon
10s of millions of impact craters
Some diameters of hundred of miles
Most impacts in 1st 700 mys, no real big impacts after 3.1bya
Evidence: no impact scars on Maria, flood basalts

4. Meteor Crater, aka Barringer Crater
Northern AZ. Winslow
50ky ago, asteroid traveling +26k mph
1 mile across, 2.4 miles in circumference, + 500 ft deep
½ of meteorite vaporized during descent, impact energy = 10 megatons
1960s NASA astronauts trained to prepare for Apollo missions
Named after Daniel Barringer, who was positive that most of the meteor was under
crater and would make him rich, at least it made his family rich

5. Most space debris are asteroids, comets are secondary
Meteoroids
Either a piece of asteroid or comet that is orbiting the sun
Asteroid
Meteoroids larger than 1 meter
Meteor
Meteoroid that comes through the Earth’s atmosphere
Shooting star, burning up, can also be deflected
Meteorite
Actually hits the Earth’s surface
Irons = metallic, most collected meteorites
Stones = rocky, most space debris that reach our atmosphere
but readily break up when it does, more susceptible to weathering
Comet
Ice, rock, dust and frozen gasses

6. Thank Goodness for Our Atmosphere
Estimated 100,000 million meteoroids hit the earth’s atmosphere every day
90-95% entirely or almost entirely burn up in the atmosphere
Estimated that 19,000 to 25,000,000 hit the earth everyday
Really depends on who is counting and how really small pieces are counted
Adds about 100-1,000 pounds of material to the surface every day
At about 70 miles from surface atmosphere is so dense, many meteoroids glow, shooting stars
Visible at 60 miles up from surface
Speed of incoming also a factor 25,000 to 70,000 mph
Huge belly flop as it hits low viscosity atmosphere, most destroyed or deflected

7. How Often Does Space Debris Hit the Earth?

10. Near Earth Objects
or NEOs
Comets and asteroids in Earth’s neighborhood
It becomes at NEO when closest approach to the sun
in less than 1.3 AU or 120,842,549 miles
As Aug. 25, 2019
20,602 NEOs have been identified
Tracking and monitoring over 16,000
If they come as close as 28 million miles from us…..
A hair’s breadth away in cosmic terms!!!!!!!!!!!!

11. Real Time Tracking
• https://cneos.jpl.nasa.gov/sentry/

12. 1.1e-5
0.000011% chance of Earth impact
99.999989% chance asteroid misses us
5.2e-8
0.000000052% chance of Earth impact
99.999999948% chance asteroid misses us
https://cneos.jpl.nasa.gov/ca/

13. Orbits of all known
Potentially Hazardous
Asteroids or PHAs as of
January 8, 2019
1,955 of which 107 are
comets

14. Potentially
Hazardous Objects,
PHOs
101955 Bennu
Diameter of 1,614 feet, average
Will come within 5 million miles or .05 AU of Earth’s orbit in 2135
Makes a close approach every 6 years on average
Approach may change its orbit
May lead to potential impact, 2175-2199
Calculated risk during this time 0.037%
Close does not equal impact
Object, whose orbit is within 4.7
million miles of Earth’s orbit, larger
than 500 feet in diameter

15. Why The Fascination
With Bennu
OSIRIS-Rex is currently looking for a parking place
Will touch surface July 2020, collect 60-2,000 grams of dirt and rocks
Samples will be packed into a capsule, will land in Utah 2023
Perfect asteroid to study, Why???
It’s close, gets even closer every 6 years almost same plane of Earth’s orbit around the sun
Perfect size, does not rotate too fast only once every 4.3 hours
Its old, and very pure, gives us insight to the solar system formation
Preserved in space’s vacuum
Carbon rich, has the chemical recipe book of early life
Rich in resources, such as iron and aluminum and platinum
Will help understand the quirky characteristics of other asteroids
Why we picked it

16. How Do We Know How Big An Asteroid Is?
Asteroid size can only be crudely estimated
Estimated absolute magnitude, brightness
Estimated albedo, reflectivity
Shape is assumed spherical
Even though is more than likely not
Working on finding 90% of NEO + 140 meters, 459 feet

17. In 1998, and 2005, Congress told NASA to find at least 90% of the NEOs
And to make plans for diverting ones that posed a risk to Earth
It is believed that +90% of 140 meters or larger NEOs have been tagged
NASA can predict the path of the orbit with some certainty for 100 years
But the path becomes more uncertain with time
As the asteroid passes by planets and other objects, its orbit changes slightly
NASA has not found an asteroid or comet that poses a realistic threat within the next 100 years
But is monitoring about 2,000 “potentially hazardous” objects
Come within 4,647,790 miles of Earth and are large enough to cause damage
The smaller asteroids are more difficult to find, and they can still be very destructive
Shine less brightly in the night sky, need to be closer to Earth to be seen
Blind spot= the Sun, if coming from direction of the sun, can’t be spotted

18. What if One
Made it
Through…
Many factors determine the amount of damage an asteroid would cause:
Size
Composition
Speed
Angle of entry
Location of ground zero

19. Duck!!!!
Example: 164 feet wide asteroid
Density of 2.6g per cubic centimeter
Traveling 7 miles per second
Hitting at a 45 deg. Angle
The most common angle of entry
Increase in entry angle = increase in damage
Smaller angle = more air resistance, explodes at higher altitude with less power
The result:
3.3 megatons of kinetic energy
Airburst energy of 2.9 megatons at 8.5 km or 5 miles above the Earth’s surface
Equal to 138 atomic bombs or 9 nuclear warheads!!!!!

20. In the News
Chelyabinsk, Russia
February 15, 2015, 9:20am meteor exploded over Chelyabinsk
Force of 30 atomic bombs
10 tons and 49-59 ft wide, traveling 33,000mph
Broke up 18-32 miles above the earth
Blast picked up on monitoring stations in Antarctica
Burned brighter than the sun
Sonic blast shattered more and 1,000,000 sq. feet of glass
3,000 buildings damaged
1,100 people injured, mostly by flying glass
Could have been worse
Industrial town with nuclear and chemical weapons disposal facilities
This size of event happens every 30-40 years

21. That Was a Close One!!!!!
February 15, 2013 2012 DA14 came within an astronomical hair’s breadth away from Earth
We knew it wouldn’t get any closer than 17,150 miles above the Earth’s surface Whew!!!!
150 feet across, estimated mass of 130,000 metric tons
Traveling 17,450 miles per hour, or 4.8 miles per second
Closer than geostationary orbit of communications satellites
Came in below, since in came in at an angle
Closest ever predicted of an incoming large object
One this big travels this close every 40 yrs
Average impact once every 1,200 years
Probably about 500,000 asteroids the same size
Less than 1% have been discovered

22. Close call, and we didn’t even see it coming!!!!
Asteroid 1989FC , aka 4581 Asclepius
.3 miles across
March 22-23, 1989, Missed the Earth by about 400,000 miles
Hit the exact spot the Earth had been only six hours earlier!!!!!!
If it had hit
Crater 4.4 miles wide
Release energy comparable to the explosion of a 600 megaton atomic bomb.
Asteroid was discovered March 31 1989….9 days after its closest approach to the Earth!!!!!!

23. K-T Impact
65 million years ago
Hit in the Yucatan Peninsula
Known as the Chicxulub Impact
Evidence: layer of iridium found around the planet 300 times normal amounts
(common in meteorites)
Bad News: Responsible to the extinction of the dinosaurs (excluding birds)
Also mass extinction of plants and other animals
Good News: Allowed mammals to become dominant
Which eventually leads to us!!!

24. During Cretaceous, Yucatan was covered by a shallow sea
Impact released 100 million megatons of energy
Equal to 300 million nuclear weapons
Impact generated wildfires
Superheated material would have started fires
Would have burned for months
Tsunami, waves heights up to 100 meters
Would have traveled all the way to coasts of Texas, Louisiana and Alabama

25. Impact just happens to hit a large gypsum formation, lots of sulfur
Also carbonate shelf there
325 gigatons of sulfur and 425 gigatons of carbon dioxide released into atmosphere
10 times global human emissions in a year all at the same time
Sulfates become nucleation sites for acid rain
Most breathing things suffocated
Plants foliage destroyed
Dissolved marine shells
Changes balance of CO2 between atmosphere and ocean, Waters become anoxic
What happens to what survives initial impacts and effects:
Dust, smoke and aerosols from impact reduces incoming solar radiation
Land plants and algal plankton can no longer photosynthesize
Lowers global temperatures by 26 deg. C.
Initially below freezing for weeks to months, up to 3 years
Greenhouse gasses then raise global temperatures

26. Not Just the DinosaursAbout 70% of all species wiped out
Almost all large vertebrates
Including dinosaurs, plesiosaurs, mosasaurs, pterosaurs
Almost all plankton
Almost all tropical invertebrates
Reef dwellers especially hard hit
Land plants decimated
Some things did survive
Insects
Mammals
Birds
Flowering plants
Deep sea marine organisms
Sharks
Some corals
Some fishes
OUT
IN

27. Effects of Extinction Level Asteroid Hit
Effects can be broken down as local, or global
Effects can be broken down by time for the effect to be felt
Immediate
Months
Years
Decades

29. What If a K/T Size Impact Hit Today?
Hits land
Large earthquake, and huge aftershocks
K/T impact most likely caused a 11.3 mag. earthquake
Regional if not global wildfires
Hits the ocean
Tsunami up to 1,000 ft. high
Large bubble of steam (120^3) miles that would send debris into the atmosphere
Hits Coastal or shallow sea
Vaporize underlying limestone, which would add CO2 to the atmosphere

30. Continued
Hits anywhere
Large amounts of nitrogen oxides released into atmosphere
Comes down as acid rain
Acidify oceans and all surface waters
Dust would block incoming sunlight
Crops would fail
Dark and winter like conditions for weeks or months
CO2 remaining in atmosphere
Increase in greenhouse gases, global warming
Melting of glaciers, rising sea levels
Drowning out any low-lying or coastal areas, millions displaced

31. Environmental Impact
In first hours and days after the impact there would a huge increase in temperature
Fireball, followed by hot gases
After that for a few months there would be an almost equal decrease in temperature
Atmosphere filled with dust and ash, blocking sun
Then warming of the planet
Greenhouse effect from CO2 that remained in atmosphere

32. NEO, Near Earth Objects
Comets or asteroids that pass within 28 million miles of Earth’s orbit, think “space distance”
Largest source, asteroids that collide and break into smaller fragments
Hit Earth at more than 100 tons a day
Most NEOs burn up or disintegrate in Earth’s atmosphere
Started tracking NEOs during the 1970s
1992, NASA begins working on “identification, characterization and tracking” of NEOs
Also, developing mitigation strategies
Predicted that by 2002 most NEOs larger than .62 miles (greatest threat size) would be identified
Didn’t quite make it we are about at 90%...................we think

33. National Near-Earth Object Preparedness
Strategy and Action Plan, June 2018
The plan has 5 overarching strategic goals to reduce the risk of NEO impacts through “
improved understanding, forecasting, prevention, and emergency preparedness.”
Sounds familiar???
The plan will:
• enhance NEO detection, tracking, and characterization capabilities
• improve NEO modeling prediction, and information integration
• develop technologies for NEO deflection and disruption missions
• increase international cooperation on NEO preparation, and
• establish NEO impact emergency procedures and action protocols

34. Planetary Defense Coordination Office
Find
“ employ a variety of ground and space based telescopes to search for NEOs, determine
their orbits, and measure their physical characteristics.”
Warn
“ responsible for providing timely and accurate information to the government, the media,
and the public on close approaches to Earth by potentially hazardous objects (PHOs) and
any potential for impact. If any PHO is found to pose a significant chance of impacting Earth
(greater than 1 percent over the next 50 years), the PDCO will provide notification
messages for NASA to send to the Executive Office of the President, the U.S. Congress, and
other government departments and agencies

35. Mitigate
“studies of technologies and techniques for deflecting an asteroid off a predicted
impact course with Earth”
Coordinate
“works with other government agencies to develop and update a National NEO
Preparedness Strategy and Action Plan. …. provides expert input on the nature and
effects of asteroid impacts to the Federal Emergency Management Agency (FEMA), so
that adequate emergency response can be prepared in the event of a PHO impact that
is not possible to avoid.”

36. Near Earth Object Observations Program
Find, track, and characterize at least 90% of the predicted number of NEOs that are +140 meters
To characterize a subset representative of the entire population
World wide use of telescopes search and track NEOs,
Determine their orbits, and gain information on their sizes, shapes, and composition
Major NEO survey projects in the NEO Observations Program include:
University of Arizona’s Catalina Sky Survey
University of Hawaii’s Panoramic Survey Telescope and Rapid Response System (Pan-STARRS)
University of Hawaii's Asteroid Terrestrial-Impact Last Alert System (ATLAS)
MIT Lincoln Laboratory’s Lincoln Near-Earth Asteroid Research (LINEAR)

37. Don’t Worry, We Have a
Plan!!! (Actually, we
don’t, we just run
scenarios and tell you
what might happen)
Planetary Defense Conference Exercise May, 2019
Annual conference, brings together NASA ESA and other experts
What if an asteroid hit Earth???
In 2018 Tokyo was saved after a nuclear bomb was used
Other years, not so much, both the French Riviera and Dhaka were destroyed

38. Time 2019
Imaginary asteroid 330-1,000 feet in diameter, 2019 PDC is on a near Earth collision course
Calculated risk, only a 1% chance of impact in 8 years
Press release was sent out with risk
Time 2021
NASA sends a probe to investigate
Headed toward impact, Denver
Time 2024
World’s space powers decide to build 6 “kinetic impactors” to ram the asteroid
Launched in 2024, 3 hit asteroid (Nuclear bomb not an option due to political fighting)
Fragments the asteroid, (165-265 feet in) now on impact course with NYC
Mass Evacuation of New York City Ordered, that’s right 8.7 million people
Time 2027
NYC has a 10 day advance notice of impending hit
Asteroid enters atmosphere traveling 43,000 mph
Explodes over NYC, blast 1,000 times more powerful than Hiroshima, NYC is obliterated

39. Small asteroids (few meters dia.) pass through Earth Moon’s orbit a few times a month
https://cneos.jpl.nasa.gov/ca/intro.html
How good are we finding NEOs
As Aug. 25, 2019, 20,602 NEOs have been identified
On average about 500 NEOs are discovered a year
About 1/2 of known NEOs are larger than 460 feet
Estimated that 66% of larger than 460 feet have yet to be discovered
Ground based telescopes are still limited
Can only survey the sky at nights with no clouds
There are no KNOWN asteroids that pose a significant
risk of impact with the Earth over the next 100 years

40. Lifetime Risk
*1 in 30,000,000 lifetime risk
Frequency vs. Magnitude
They don’t happen often, but when they do their impact is HUGE
We tend to remember only the extraordinary
events, such as the odd coincidences: but we forget
that almost every event is an odd coincidence. The
asteroid that misses the Earth is on a course every
bit as improbable as the one that strikes it.
Arthur C. Clarke
*Tunguska
size event

41. Lifetime Risk Continued
Average interval between impacts 500,000 years
Annual probability a person will be killed 1 in 500,000
Assumed fatalities from impact ¼ of human population
Total annual probability of death 1 in 2,000,000

42. Possible SolutionsCall Bruce Willis
Attach a rocket to knock it slightly out of orbit
More difficult technology wise than going and returning to the moon
Hayabusa probe landed on asteroid Itokawa in 2005 by Japan
Gigantic reflective surface to vaporize it
(the Germans actually designed such a weapon in WW2)
Removing some of its rock mass
Gravity tractor
Blowing it up with a nuclear explosion
Used if discovery is too late for other options, should be last resort
We will see on Friday the 13th (not making this up) 2029 or Easter Sunday in 2036

43. Some people have claimed to have been hit by meteorites
Very rare
Often unproven
First unsubstantiated account
1911, Egypt
Dog was reported killed by a “Martian meteorite”
Only confirmed person in history
Ann Hodges, Alabama, 1954, about 9 pounds
Crashed through her ceiling, bounced off a radio,
then hit her
Just suffered a bruise…a really big one

44. • End