Phobos, moonof Mars

It’s a tough neighbourhood out there….

Mercury

Moon

Moon

Can see pathways of ejecta… (false color to highlight)

Moon up close from Apollo

where would you land?

Mars

Mercury

Venus

Earth’s Moon (S. Pole)

Earth looks a little different!

But there are known impact sites

Why in these locations?

Russian meteor from 15th February, 201310,000 tonnes, 17-20 m diameter, 18.6 km/s (67,000 km/h)500 ktonnes of TNT (2100TJ) (Hiroshima 12.5kt TNT))

Shockwave hit Chelyabinsk 2.5 minutes later, and injured 1500 people,

Shockwave recorded in Antarctica (went twice round the world)

16hrs later a 30m asteroid (2012 DA14) passed within 17,000 m of Earth.

Ann Hodges was napping on her living room couch on Nov. 30, 1954, when a meteoroid crashed through the ceiling and smashed her radio. It struck her on the arm and hip, leaving her bruised but able to walk.

The meteor, it turned out, had made a fireball visible from three states as it descended on her Sylacauga, Ala., home. It’s now on display at the University of Alabama — it’s about the size of a grapefruit and weighs 12 pounds.

80 million trees knocked down over 2,150 square kilometres (830 square miles

Tunguska Event, 1908, Russia

Tunguska Event 1908

Equivalent to a 100 MT Nuclear Bomb Blast

(Hiroshima = 12.5 kt; all of WWII = 3 MT)

A manuscript published at Tortona, Italy, in 1677 tells of a Milanese friar who was killed by a meteorite:

“All the other monks of the convent of St. Mary hastened up to him who had been struck, as well from curiosity as from pity, and among them was also the Canon Manfredo Settala. They all carefully examined the corpse, to discover the most secret and decisive effects of the shock which had struck him; they found it was on one of the thighs, where they perceived a wound blackened either by the gangrene or by the action of the fire. Impelled by curiosity, they enlarged the aperture to examine the interior of it; they saw that it penetrated to the bone, and were much surprised to find at the bottom of the wound a roundish stone which had made it, and had killed this monk in a manner equally terrible and unexpected.”

One known(ish) fatality

Mistastan Lake, New Foundland, Canada 28 Km 38,000 years

All diameters are for the crater (not the impactor)

Barringer Meteor Crater, AZ 1.18 km 49,000 years

(thought to be ~50m asteroid)

Wolf Creek, Australia 0.875 Km 300,000 years

Bosumtwi, Nigeria 10.5 Km 1.3 Million years

Roter, South Africa 2.5 km 5 Million years

Karakul, Tadjikistan 45 Km < 10 Ma

Chicxulub, Mex

170 Km 65 Ma

Sufficient to penetrate the crust:

Maximum Cavity Depth ~1/3 of diameter of crater

Clearwater Lakes, Sask.

32 km/22km 290 Million years

(double impact)

Deep Bay, Sask.

13 km 100 Million years

Gosses Bluss, Australia 22 km 142.5 Million years

Aorounga, Chad 17 km 200 Million years

Note concentric rings – various theories

Aorounga, Chad 17 km 200 Million years

Manicougan Lake, Quebec 100 km 212 Million years

Formation of the moon?

Collision of Earth + Mars-sized object (re-touched somewhat)

Radar Image of NEO 1999JM8

Missed Earth by 5 million km in 1990, 6 million km in 1999

Average diameter 3.5 km

Typical menacing rocky asteroid (comets also have ice in them, and tails)

Calculated from counting moon craters , and dating From Apollo samples

Cratering over time in innerSolar system

Heavy early bombardmentthen significant reduction

How often do these thingshappen?

Note power law relationshipIf S = size of blast, f = frequency

Plots as a straight line on log-log axes

(note reversed x-axis above)

What is wrong here?

Apollo 14 site spherules

(~ 0.2 mm diameter)

Argon40/Argon39 dates

(accuracy ~ +/- 200 MY)

Glass spherules created at time of impact-dated from decay of ArgonWhy the recent increase in the last 500Ma?

Knock something out of the Oort Cloud, and we might be in trouble…

Apollo 14 site spherules

(~ 200 micro-meters diameter)

Argon40/Argon39 dates

(accuracy ~ +/- 200 MY)

26 Ma periodicity (dodgy)

Claim is that extinctions happen with that periodicity?...

Is nemesis out there?

1 BY averaging bins

Black and opaque spherules only

(the ones most definitely related to impacts)

A couple of slides back it looked light an upsurge in impacts recently,But it depends on how you process the data…

Question: If cratering rate on Earth is same as our Moon, why are their so few craters preserved?

Answer: Erosion