Lake Cuitzeo, located in the state of Michoacán, Mexico, holds evidence of an extraterrestrial impact (materials not created on earth), dating from the late Pleistocene, between 12,700 and 11,500 years ago, specifically from a period called the Younger Dryas or Younger Dryas.

This could be discovered thanks to the fact that, like many lakes in Michoacán, Cuitzeo maintained a layer of water that protected everything that entered and was deposited on its bottom. Successive layers of different materials buried older remains, preserving them in a sort of time capsule.

Meteorite debris is among the most exotic materials that can enter bodies. In Mexico there are numerous sites where these materials have fallen; the most notorious example was the meteorite that hit the Yucatan Peninsula 65 million years ago, forming a crater 10 km in diameter that is now partly covered by the waters of the sea.

There is evidence of the existence of a period of great climatic change on Earth between 12,900 and 11,500 years ago when the warming that dominated the post-glacial period was interrupted to give way to a severe cooling that persisted for about 1,300 years. This period has been called Younger Dryas because it was characterized by a large flowering of a species called Dryas octopetalus that replaced the arboreal vegetation that populated the forests before its appearance.

This abrupt global change has been previously associated with the precession cycles of the Earth's spin axis, called Milankovich cycles, or with the destabilization of the Laurentide ice that generated a change in the patterns of marine and atmospheric circulation and, therefore, of the global climate.

It is considered that the cause of climate change 12,900 years ago was an object or shower of cosmic impacts (meteorite, comet, or another object) that collided with the earth at high speed, completely modifying the landscape that we observe today in the lake basins and catalyzing the destabilization of the climate. This theory, proposed by a group of researchers in 2007, suggests that 35 species of mammals and 19 genera of birds and numerous plants became extinct, resulting in a major ecological reorganization. The most important connotation is that this impact may have contributed to a decrease in temperatures and a decrease in flora and fauna worldwide.

The cosmic object, several hundred meters in diameter, presumably fragmented into several thousand rocks rich in heavy metals such as nickel, iron, and iridium. These particles entered the atmosphere through several collision fronts with the atmosphere at velocities over 20 km/second. The presence of a crater is not observed since this material impacted the earth at a very low angle.

In addition to the high velocity, high pressure, and expansive thermal surges resulting from the aerial detonation, a shock wave was produced. The shock wave generated hypoxia (oxygen deficiency) and displaced and lifted the water from the lakes and most of the living beings, as well as melting sediments from the same surface deposits in its radius of influence.

Successive combustion generated large quantities of carbon and soot. These extraterrestrial materials may also have caused an increase in lake levels for a short period. Finally, a cloud of dust and water covered the atmosphere producing a temperature decrease of more than 7 degrees for about 1700 years.

Several pieces of evidence help us to determine the presence of extraterrestrial materials, coming from the impact of a comet or asteroid that are observed in the fine deposits of materials on Earth. The most common characteristic is their shape, either spherical, drop-shaped with dendritic ornamentation or in the form of segments or patches, which is atypical of a product derived from volcanism.

The second characteristic is the presence of nanodiamonds, which are nothing more than very small diamonds. The nanodiamonds are formed by the effect of the high pressures and temperatures generated during the impact that convert the graphite of the earth into nanodiamonds with hexagonal structure.

The evidence of this event was buried for thousands of years in the center of Lake Cuitzeo and was observed through the detailed study of a 27-meter core of sediments previously extracted. The finding was accidental, through the observation with a microscope of abundant pollen and diatom remains in the materials of this core.

Previously, the researchers involved in this ongoing research had noticed some abrupt changes in the algal community diversity, which suggested to us that some important phenomenon had occurred. Among other things, we noticed that diatom communities shifted from shallow-water, relatively transparent flora to deep-water flora.

In one of the strata a carbon level almost 10 cm thick was observed. Almost 2055 spheres per kilogram rich in carbon macroparticles and hexagonally symmetric nanodiamonds were counted, which are not found in either the stratum above or below this marker level. This quantity is among the largest found at sites where the Younger Dryas boundary is observed in the world.

These mineralogical associations do not resemble any known terrestrial process. It has been compared with those found in volcanic materials and also with possible industrial slag spherules, finding that they are different both in their mineralogy and in their structures typical of rapid cooling. The conclusion is that the spheres found several meters below the floor of Lake Cuitzeo cannot be similar to those of volcanic origin or derived from industrial processes.

In summary, none of these comparisons resembles what was observed; these markers are unique and unrepeatable and finally, they find associated a carbonized biomass with nanodiamonds that have only been observed in materials of extraterrestrial origin, so we consider this finding to be another evidence of this event.

By Dr. Isabel Israde Alcántara, a specialist in stratigraphy and paleoenvironments. She did her Ph.D. in stratigraphy at the University of Milan-Italy, specializing in diatom analysis at the University of Paris Sud. Source: Saber Más