Contact Information:

NEWS:

Our new work suggests that life not only could have survived the Late Heavy Bombardment, certain microbial communities would have thrived in the high temperature environments created by massive impacts. For more information about this, please see below.

Link to the Nature News and Views piece on our Late Heavy Bombardment paper (21 May 2009) by Dr. Lynn Rothschild of the NASA Ames Research Center.

Recent Themes and Links to Related Published Work (2006-2009):

Microbial habitability of the Hadean Earth The postulated Late Heavy Bombardment of asteroids and comets to the inner solar system had a profound effect on the thermal, climatic and biological evolution of the early Earth, Mars and Venus. To explore this further, we constructed a detailed thermal model of the Earth as a whole during the bombardment epoch ca. 3.95 billion years ago. The results of our analysis shows that under no circumstances was global sterilization reached during the bombardment. This obviously bodes well for the survival of a "deep, hot biosphere" from the most ancient times. Life's origin on Earth could well have occured as far back as 4.4 billion years ago, and this biosphere would have survived and subsequent thermal assualts from impacts.

Pre-3.75 billion-year-old sedimentary rocks in northern Quebec In the late 1960s and early 1970s, geologists discovered the pre-3.7 billion-year-old Akilia association and Isua supracrustal belt rocks in West Greenland. These discoveries forever changed our views of the establishment of the habitable Earth, but the outcrops were nevertheless confined to parts of Greenland and coastal Labrador. In 2001, Canadian geologists discovered rocks as old as 3.8 billion years in northern Quebec. We have recently provided detailed documentation of the geology of a small part of this "new" old terrane termed the "Nuvvuagittuq Supracrustal Belt" or "NSB". Ongoing work by our group seeks to shed additional light the ages and origins of these rocks ( see our recent work on the metamorphic histories of the NSB rocks).

It may now be possible to test global models for chemical change in the earliest Archean (see also our work with N. Dauphas on Fe-isotopes in the NSB rocks).

Widespread supracrustal rocks in southern West Greenland We explore the oldest geological records that provide hints about the nature of the surface environment of Earth in the first billion years. Every year more and more pre-3.6 billion year old rocks of sedimentary origin are discovered. This means that our understanding of this pivotal time period will surely continue to grow.

Geology, age & origin of the oldest known sediments All rocks older than ~3.5 Ga have been severely metamorphosed. The oldest rocks of probable marine sedimentary origin that we know of are on Akilia (island) in West Greenland. We and our collaborators have explored these in great detail.

Multiple sulfur isotope analysis of Paleoproterozoic sulfur How did the surface redox state of the Earth change in the Paleoproterozoic in response to changes in oxygen concentration in the atmosphere that in turn drove changes in metabolic styles of life?

Hadean zircons and the thermal history of crust on the earliest Earth Our research has shown that the oldest terrestrial zircons preserve domains that record thermal events to the crust which pre-date the actual rock record on Earth and may be related to impact effects.

Geochemistry of the oldest terrestrial zircons Combined REE modeling, Ti-in-zircon thermometry, Oxygen isotopes and other analyses of Hadean zircons show that they are overwhelmingly the products of normal igneous melts.

Links to some of our collaborators:

Australian National University, Research School of Earth Sciences

Center for Applied Geoscience, University of Tuebingen

Centre de Recherches Petrographiques et Geochimiques

UCLA Ion Microprobe Facility

Department of Earth & Environmental Sciences, RPI

Laboratoire de Sciences de la Terre, Ecole normale superieure de Lyon

Department of the Geophysical Sciences, University of Chicago

Department of Space Studies, Southwest Research Institute

Geophysical Laboratory, Carnegie Institution of Washington

Courses Offered:

GEOL 1020: Introduction to Geology 1 (offered Summer session 2007)
GEOL 1020: Introduction to Geology 2 (next offered Spring 2010)
ASTR/GEOL 3300: Extraterrestrial Life (last offered Fall 2008)
GEOL 4500: Critical Thinking in Earth Sciences: Origin of Life (some years)
GEOL 4700/5700: Archean and Proterozoic Geology (some years)
GEOL 5700: Cosmochemistry (next offered Fall 2010)
GEOL 5700-006: Planetary Field Geology (co-taught with Prof. B. Hynek, Fall 2009)
ASTR/GEOL 5835: Planetary Seminar - Planets and water (Spring 2010)

Journals: