Natural Disasters and Family Misfortunes 18: Comets & Meteorites

We occasionally get news reports of meteorites that come close to Earth as they move through the solar System. One such case was in July of this year when a comet apparently came within 40,000 miles of our planet. For reference, the Moon is 238,900 miles from Earth. Asteroid 2016 D, a 450-foot wide rock, was entirely missed by scientists as NASA, who track these things, until it was almost on us. Had it struck, it would have produced an event the size of about 30 atomic bombs.

Path of comet 2019D (retrieved 2 October 2019 from https://www.thesun.co.uk/tech/9968765/nasa-asteroid-earth-missed-bad-weather/

Over the past twenty years, 556 asteroids have entered the Earth’s atmosphere.  Most of them burn up before hitting the ground – the fireball called a bolide – but the Earth has seen a few larger ones strike the surface with devastating consequences.

This diagram maps the data gathered from 1994-2013 on small asteroids impacting Earth's atmosphere to create very bright meteors, technically called "bolides" and commonly referred to as "fireballs".  Sizes of red dots (daytime impacts) and blue dots (nighttime impacts) are proportional to the optical radiated energy of impacts measured in billions of Joules (GJ) of energy and show the location of impacts from objects about 1 meter (3 feet) to almost 20 meters (60 feet) in size. Image Credit: Planetary Science (retrieved 2 October 2019 from https://www.jpl.nasa.gov/news/news.php?release=2014-397)

Humans have always been fascinated with heavenly bodies, raising some appearances to almost religious worship status. They have both amazed and frightened people for centuries, studied by scientists and philosophers alike. Even liked to diseases and witchcraft! The presence and path across the skies have been featured in books and drawings for centuries.

A depiction of the Great Comet of 1577 over Prague by Jiri Daschitzsky; In addition to the comet, five zodiac symbols appear in the sky: (L-R) Aries, Pisces, Aquarius, Capricorn, and Sagittarius. Below the comet's tail are the crescent moon and Saturn, depicted as a star with the astronomical  symbol ♄. At the bottom center, a man draws the comet by the light of a lantern. (retrieved 2 October 2019 from commons.wikipedia) 

Comets and meteorites striking Earth have been topics of conversation and scientific research projects for thousands of years. We readily see the evidence of comet-strikes on the face of the Moon. On Earth they are more subtle, modified by erosion and covered by vegetation, and in some cases, by ice. One collision favoured by geologists annihilated dinosaurs about 65 million years ago when a comet, estimated at over 6 miles in diameter, struct near what is now the Yucatan Peninsula resulting in a crater (the Chickxulub Crater) 110 miles wide. https://en.wikipedia.org/wiki/Chicxulub_crater The gases and debris thrown into the atmosphere caused masked the Sun for probably decades, changing the climate through acid rain and excessive cooling which choked out life around the world.

Modern geophysical tools are able to reveal the locations and size of the impact area.

Location and gravity anomaly maps of the Chicxulub impact area. The coastline is shown as a white line. A series of concentric features reveals the location of the crater (retrieved 2 October 2019 from https://commons.wikimedia.org/wiki/File:Chicxulub-Anomaly.jpg)

Beneath the ice sheet in Greenland is a massive, 20-mile wide crater thought to have been created by a mile-wide asteroid colliding with the Earth about 13,000 years ago. Human civilization had yet to be developed but such an event could have resulted in death and destruction of animal life in the Northern Hemisphere and a disruption in the migration of humans into Europe and North America.

Left: Ice-penetrating radar disclosed a possible crater under a Greenland glacier; right: map showing location of impact crater under Hiawatha Glacier (images retrieved 2 October 2019 from https://www.sciencenews.org/article/greenland-impact-crater-top-science-stories-2018-yir)

Often these astroblemes are regions where mineralogy has been changed. In the Sudbury, Ontario, Canada, region the impact of a 6 to 9-mile wide bolide over 1.8 billion years ago (Palaeoproterozoic) resulted in a basin 20 by 40 miles in size. Rock fragments thrown up have been found thousands of miles away. The crater filled with magma, probably from the Earth’s mantle which contained valuable minerals and precious metals. Deposits have been mined since the 1880s.

Left: NASA World Wind satellite image of the Sudbury astrobleme in Ontario, Canada; right: geological map showing the Sudbury Basin, produced by Natural Resources Canada in 1955.

We don’t have definitive reports of widespread death and destruction in the written historical record, but there are stories that go back thousands of years that might reflect these types of events.

The destruction of Sodom and Gomorrah is now thought by scientists studying Jordan’s Tall el-Hammam area to be an historical account of an impact from a meteor that struck about 3,700 years ago. The meteor probably exploded at low-altitude, wiping out villages and farms and rendering the region uninhabitable for several centuries.

The Destruction of Sodom and Gomorrah, by John Martin, 1852; original oil painting on canvas at Laing Art Gallery, Newcastle upon Tyne, UK (image retrieved 2 October 2019 from https://en.wikipedia.org/wiki/The_Destruction_of_Sodom_And_Gomorrah#/media/File:John_Martin_-_Sodom_and_Gomorrah.jpg)

Over 40,000 people may have been killed instantly in the blast. Fertile soil would have been baked, losing all nutrients through the heat and a following tsunami-like flood of salt water from the Dead Sea. All structures would have been levelled.

Further back in time, the ancient city of Akkad may have been destroyed by a comic asteroid impact during what has been named the 4.2 kiloyear event. During the time following, climate cooled, drought persisted in most areas of the Northern Hemisphere lowering food production, societies collapsed, and social chaos prevailed.

Akkad was the centre of one of the earliest human civilizatons in Mesopotamia. Joachim Seifert and Frank Leske are the authors of a paper titled The Destruction of the City of Akkad by a Cosmic Asteroid Impact and the Link to Global Climate Change, published online in 2013 (http://www.flarchives.co.uk/uploads/1/9/7/5/19752675/akkad_paper.pdf). They assert that the city was completely destroyed by meteorite strikes, as apparently even described and recorded by others in the region as “giant dust plume soaring over Mesopotamia.”

Map showing impact locations in Mespotamia around 2200 BP (Akkad was located immediately to the right of the impact labelled Umm-al-Binni)

Geological and archaeological evidence, along with written accounts support the impact interpretation. The region was apparently struck by several meteorites, probably fragments of a much larger cosmic body. A larger piece may have been responsible for the Umm al Binni Lake crater located next to the old city of Akkad.

So, what does this have to do with genealogy. Not much other that to indicate that people were impacted by these types of evets and could be again, as we have seen from the near misses. Within the most recent centuries, meteors or bollides, were observed with trepidation. In that respect they became symbols of mayhem. Any large meteorite hitting the Earth would cause significant damage and death, as they did in the examples shown above.

Hundreds of impact locations have been found to date. With improved technology many more are likely to be discovered. We may even find a few events that occurred during the last few hundred years that our ancestors might have experienced.