On March 1, 2005,The Research Vessel Maurice Ewing sailed from Progreso, Mexico, having completing a research mission that began in Panama on January 7th.

An international team of scientists from the Instituto Geofisica of the Universidad Nacional Autonoma de Mexico (UNAM), the University of Texas Institute of Geophysics, and the University of Cambridge and Imperial College of London in the United Kingdom participated in this six-week research mission examining the Chicxulub crater. The Chicxulub Crater is located on the north side of the Yucatan Peninsula with the center of the crater at the present day resort and fishing town of Chicxulub. The crater is approximately 120 miles in diameter—almost the distance from Washington, DC to New York City.

This research program collected data from more than 1,130 miles along the ship’s route across the crater -- more than five times the distance surveyed during an earlier cruise. Scientists collected two types of data—reflected-sound data that is received by the 3.6 mile long streamer towed behind the ship, and refracted sound data received by seismometers positioned across the crater both underwater and on land. Scientists then used this data to develop a 3D image of the crater impact.

This cruise yielded new data that is expected to significantly increase understanding of the Chicxulub Crater:

• Greater understanding of the process of an extraterrestrial body impacting earth, a process that helped to shape our planet in its early millennia. If such an impact occurred today, it would have disastrous effects on earth and its inhabitants. However, such impacts are infrequent. A 2003 NASA study estimated that about 1,100 near-earth objects (NEAs), including asteroids, larger than .62 miles (3,281 feet) could hit the earth once in 500,000 years. Still, given the devastating impact of such an object, NASA continues to monitor NEA activity.
• Increased knowledge of which aspects of the impact caused mass extinctions, and specifically how the Chicxulub Crater impact caused the extinction of the dinosaurs. Scientists speculate that the impact caused fires, tidal waves, high winds, earthquakes, volcanic activity and trillions of tons of debris added to the atmosphere resulting in months of darkness and decreased temperatures and eventually acid rain, loss of vegetation, death of large herbivores and then large carnivores. It is worth remembering that neither humans nor marine mammals would be on the planet today if it were not for this event that killed many large reptilian predators and ushered in the age of mammals.
• With over a half million people now living on the site of the Chicxulub Crater, understanding its structure takes on increased importance. For example, the structure of the impact crater is directly tied to the hydrogeology of the northern Yucatan—a primary influence on the subsurface water is the presence of the underlying Chicxulub Crater and the fracture patterns created in the surrounding rocks by the impact itself. Since these fracture systems act as conduits for groundwater circulation, understanding the structure of the crater is considered by experts such as Mario Rebolledo-Vieyra, Director de la Unidad Quintana Roo for the Centro de Investigacion Cientifica de Yucatan, to be the key to understanding the groundwater resources. In addition to fresh groundwater, the Chicxulub Crater extends beneath the Gulf of Mexico, a source of salt groundwater, with a certain amount of salt water coming into the land. These same fractures offer pathways for salt water intrusion and present the potential for pollution into this area of the Yucatan.

Throughout the Ewing cruise, operational procedures were in place designed to insure the safety of marine mammals and no marine mammals were endangered. These procedures were carried out by a team of trained marine mammal observers monitoring an area around the ship when multi-channel seismic operations were being conducted. This monitoring of the safety radius included use of special high-powered binoculars, as well as towed sonar array used to listen for marine mammals. LDEO is recognized as a leader in the development and implementation of marine mammal mitigation.

One unfortunate incident did occur Monday night, February 14, 2005, when the research vessel went aground while maneuvering at low speed 35 nautical miles from Progreso. There was no damage to the vessel. The cause of the grounding was related to the insufficient information available on the navigation charts used. Later that week, on completion of the research mission, the Ewing entered the port of Progreso to assist the Mexican authorities with their inquiry into the cause of the ship grounding. Following discussions with PROFEPA, the Mexican environmental agency, an agreement was reached to provide $200,000 for the restoration of the seafloor in the area of the grounding.

Chicxulub History 

When the impact that created the crater occurred, several miles of crust completely vaporized, creating a temporary 21-mile deep hole in the crust down to the mantle. The hole was refilled as its center rose up, akin to the water’s response to a rock thrown in a pond, while at the same time the sides of the crater were collapsing inwards. The final depression in the surface of the earth that was left behind was between 1,300 to 3,200 feet deep. All of this occurred within the span of five minutes.

The far-field effects included a tsunami that reached as far north as a couple of hundred miles inland in Texas and the laying down of a layer of glass spherules, which was as thick as several feet through Mexico, Belize, Hispanola and Cuba and dusted the entire earth with exotic minerals such as iridium from the impact. Most extraordinary, 70 percent of the species on the planet went extinct. Also of interest is that although oil is now found outside the crater, there is none inside the crater because all of the oil producing rocks and reservoir structures were completely disrupted by the impact.

The National Science Foundation owns the RV Ewing, which is operated by the Lamont-Doherty Earth Observatory (L-DEO).

Mariellen Gallagher
Director of External Affairs
Lamont Doherty Earth Observatory