Question

Some researchers contend that the end-Permian extinction event was caused by an impact with a large extraterrestrial object. Describe three forms of evidence that you would like to see before you accept this hypothesis.

Short answer

To accept the hypothesis that the end-Permian extinction event was caused by an impact with a large extraterrestrial object, I would like to see the following three forms of evidence: 1. Geological: The presence of a large impact crater dating back to the same time as the extinction event, signs of a massive tsunami or similar water disturbances, and a sharp increase in sedimentation rates or unusual sediment layers from the same period, suggesting a sudden and disruptive event. 2. Paleontological: A sudden and dramatic decrease in biodiversity in the fossil record at the end-Permian boundary, evidence of selective extinction patterns, and identification of rapid ecological and environmental changes within the fossil record, such as sudden shifts in dominant plant or animal species within various ecosystems. 3. Geochemical: Iridium anomalies in end-Permian rock layers, high concentrations of shocked quartz or other minerals typical of impact events, and isotopic patterns in rock layers from the end-Permian boundary indicating rapid climate change or other large-scale environmental shifts consistent with an impact event.

Step-by-step solution

1. Find Impact-related Geological Evidence

To support the hypothesis that the end-Permian extinction event was caused by an impact with a large extraterrestrial object, we would need to identify specific geological evidence that is indicative of such an event. This could include: - Identifying a large impact crater that dates back to the same time as the extinction event. - Finding evidence of a massive tsunami or other large-scale water disturbances that could have resulted from an impact event. - Observing a sharp increase in sedimentation rates or unusual layers of sediment from around the same time, suggesting a sudden and disruptive event.

2. Find Paleontological Evidence

In order to further support the hypothesis, we would need to look for paleontological evidence that suggests a rapid, mass extinction event. This could involve: - Examining the fossil record for a sudden and dramatic decrease in biodiversity at the end-Permian boundary. - Looking for evidence of selective extinction patterns, where certain types of organisms were more severely affected than others, which might be consistent with an impact event causing different biotic stresses. - Identifying rapid ecological and environmental changes within the fossil record that could be associated with an extraterrestrial impact, such as a sudden shift in the dominant plant or animal species within various ecosystems.

3. Find Geochemical Evidence

Lastly, we would need to find geochemical evidence that supports the possibility of an extraterrestrial impact at the end-Permian boundary. Examples of such evidence could include: - Discovering iridium anomalies in rock layers that date back to the end-Permian event. Iridium is an element that is rare on Earth but commonly found in meteorites, so its presence in significant quantities could be indicative of an extraterrestrial impact. - Finding high concentrations of shocked quartz or other minerals that are typically associated with the intense pressures and temperatures generated during an impact event. - Analyzing isotopic patterns in rock layers from the end-Permian boundary, looking for evidence of rapid climate change or other large-scale environmental shifts that could be consistent with an impact event.

Key concepts

Impact-Related Geological Evidence

The possibility that the end-Permian extinction, also known as the Great Dying, was influenced by an extraterrestrial impact has intrigued scientists for decades. Let's start with the most direct piece of evidence: impact-related geological evidence. Imagine the Earth's geology as a vast recording device of historical events. To subscribe to the impact hypothesis, one would expect to find a distinctive signature left behind by such a catastrophic collision.

If a large extraterrestrial object had collided with Earth, it would likely have left behind a large impact crater. Identifying this crater, appropriately dated to about 252 million years ago, would be a significant step towards proving such an event occurred. Moreover, geologists also search for secondary evidence such as tsunamis and massive sedimentary deposits, which are aftermath effects of an impact. These can create distinctive, abnormal geological layers known as ejecta blankets that radiate away from the impact site.

Additionally, traces of shocked quartz—a form of quartz that has been structurally transformed by intense pressure—and other high-pressure minerals like stishovite or coesite, commonly found at known impact sites, would provide compelling corroboration. These minerals are rarely formed by terrestrial processes and typically indicate a violent extraterrestrial event.

Paleontological Evidence

Moving on to the evidence embedded within the earth's former inhabitants, the paleontological evidence is paramount in unraveling the secrets of the end-Permian extinction. Paleontologists, like detectives, scrutinize the fossil record for clues to past life and sudden changes in it. A dramatic decline in biodiversity captured in the rock strata precisely at the Permian-Triassic boundary would support a catastrophic event theory.

Given that impacts can induce selective pressure, we often find patterns where certain species are wiped out while others endure. If such patterns from the end-Permian reflect a drastic event, that would possibly bolster the impact hypothesis. An example would be a disproportionate disappearance of photosynthetic organisms due to a resultant shadowing effect blocking the sun's rays. Moreover, an examination of the ecological and environmental disruptions, like altered food chains or a shift in dominant species, would tell us much about the nature of the extinction. For instance, a sudden disappearance of predatory marine species in the fossil record could reflect the chaos an impact would inflict on ocean ecosystems.

Geochemical Evidence

To round out the trifecta of evidence that might point to an extraterrestrial trigger for the end-Permian extinction, we consider the geochemical evidence. Geochemical fingerprints are like the unique DNA of cosmic events and can indicate the presence of extraterrestrial material on Earth. The discovery of an anomalously high concentration of iridium—rare on Earth's crust but common in meteorites—in the geological layer corresponding to the end-Permian supports the idea of an impact.

But there's more than just iridium. Evidence of shocked quartz and other telltale high-pressure minerals, as mentioned earlier, also contribute to the geochemical portfolio of evidence. Furthermore, by examining the isotopic compositions of certain layers, we can infer ancient temperatures and perhaps identify a sudden climate shift which might result from an immense dust cloud thrown up by an impact, blocking sunlight and disrupting the climate. Scientists specifically scrutinize the isotope ratios of oxygen, carbon, and other elements to trace these ancient environmental shifts. While climatic variations are common throughout Earth's history, seeking an extremely rapid change would back the theory of an abrupt, catastrophic event like an extraterrestrial impact.