Start of the Chicxulub Drilling Project in Yucatan, Mexico
On December 3, a scientific deep drilling projects starts on the Yucatan
Peninsula, Mexico into the Chicxulub crater that was formed some 65 million
years ago by the impact of an asteroid, which is believed to have caused the
extinction of the dinosaurs and other species. In the opening ceremony the
governor of the province of Yucatan, Patricio P. Laviada and the President
of the Autonomous University of Mexico, Juan R. de la Fuente will
participate as well as numerous scientists, engineers, and regional
politicians. The German delegation consists of
the German ambassador to Mexico, Dr. Wolf-Ruthart Born and Prof. Rolf
Emmermann, chair of the executive board of the GFZ Potsdam. Prof. Emmermann
is also the chairman of the International Continental Scientific Drilling
Program (ICDP) which sets up the organizational framework of the Chicxulub
Project.
This drill site named Yaxcopoil-1 (YAX-1) is situated 40 kilometers
southwest of the province’s capital Merida. It is intended to give insight
on the one hand into the size and material properties of the projectile, the
amount of released impact energy, the structure of the crater and the
physico-chemical processes related to the impact. On the other hand, the
research aims at the effects of this catastrophic event on environment and
life on Earth.
Chicxulub and the Cretaceous-Tertiary Boundary
About 65 million years ago at the boundary between the Cretaceous (the last
geological period of the Mesozoic) and the Tertiary eras, a large asteroid
came rushing out of space at a velocity of more than 25 km per second and
impacted the Earth at the tip of the Yucatan platform. The enormous amount
of energy generated by this impact, equivalent to 10 thousand times the
world’s nuclear arsenal, ejected into the atmosphere huge quantities of dust
particles and gases. The asteroid with a diameter of more than 10 km
impacted into a shallow ocean and penetrated the Earth’s crust down to a
depth of several kilometers. It vaporized, melted and shattered ocean water
and the Yucatan target rocks composed of carbonate and sulphate. As a
result, a crater some
200 km in diameter formed. Over a short period of time (a few minutes)
several hundred billion tons of CO2, SO2 and water vapor released by the
vaporized target rock were injected into the Earth atmosphere. An abrupt and
global perturbation of the Earth System followed: the climate became
unstable, the fine dust suspended in the atmosphere blocked sunlight,
decreasing or even stopping photosynthesis. This ecological catastrophe is
believed to have caused the famous Cretaceous-Tertiary (KT) boundary mass
extinction which saw the demise of the dinosaurs and more than 50% of the
Earth fauna and flora on land and in the oceans.
The hypothesis that an asteroid or comet impact induced the mass extinction
at the KT boundary was first proposed in 1980 by a team from the University
of California at Berkeley led by Nobel price laureate physicist Luis Alvarez
and his geologist son Walter. Very controversial at first because of its
catastrophic aspect, this hypothesis was confirmed in the early 1990’s when
scientists realized that the impact structure which lay buried under
approximately 1 km
of Yucatan platform sediments was in fact the long-sought KT boundary crater
predicted by the Alvarez hypothesis. This huge bowl-shaped structure,
centred at Puerto Chicxulub near Merida is clearly outlined by gravity and
magnetic geophysical anomalies. It had first been identified as a potential
impact crater by geophysicists Antonio Camargo-Zanoguera and Glen Penfield
while exploring the potential oil reserves of Yucatan for Pemex. The
structure had been drilled, although unsuccessfully for oil. In the early
nineties, studies of the recovered core samples confirmed that the Chicxulub
structure was indeed a huge impact crater.
Dating of the impacted lithologies indicated that it was precisely of KT
boundary age, coeval with the mass extinction. Exactly how the Chicxulub
impact induced the perturbation of the Earth System and the mass extinction
of organisms is not yet fully understood. The study of the crater and its
internal lithology in the framework of the ICDP scientific deep drilling
project will provide answers to this fundamental question.
Cratering: an important process in the formation of planets
The ICDP deep drilling project in the Chicxulub crater will also help Earth
scientists to understand better the mechanisms of crater formation.
Cratering is a key process in formation and evolution of the rocky planets.
With a diameter of approximately 200 km Chicxulub is one of the largest and
best preserved craters on Earth. Chicxulub can thus serve as a proto-typical
and accessible large planetary impact structure providing key information as
to the formation and early evolution of Earth and both dry (Moon, Mercury)
and volatile-rich planets (e.g. Venus).
Further information
A high resolution picture of the structure of the magnetic field of the
Chicxulub crater can be found at:
http://www.gfz-potsdam.de/news/foto/chicxulub/
More information is available on the internet at:
IMAGE CAPTION:
1D- and 3D-images of the magnetic anomalies of the inner Chicxulub crater
ring compiled from aeromagnetometry measurements of the GFZ aero-campaign
“MEXAGE” (Mexico Aerogeophysical Experiment).
The anomalies are sharply bounded within the inner crater. Long-wavelength
anomalies are generated by larger melt bodies deeply buried in the crater,
short-wavelength anomalies are caused by overlaying breccia. (Graphics: U.
Meyer, GFZ Potsdam)
