W A N T E D : Y O U R E - M A I L A D D R E S S : P l e a s e s e n d y o u r e - m a i l a d d r e s s t o r w s e l d e n @ r c i . r u t g e r s . e d u s o w e c a n k e e p y o u u p - t o - d a t e o n t h e M u s e u m ' s a c t i v i t i e s .

............................................ FALL 2004 Editor: R. William Selden, Collections Manager _rwselden@rci.rutgers.edu_ (732) 932-7243

MARS: The Latest Discoveries

Dr. Matthew Golombek, Rutgers’ 76 Geology, in front of gantry for the launch of the latest mission to Mars.

Last December the landings of the rovers “Spirit” and “Opportunity” on Mars began a new phase in the exploration of that planet. Jet Propulsion Laboratory scientist, Dr. Matthew Golombek, Rutgers’ 76 Geology, was responsible for selecting the landing sites for both rovers and will present the latest discoveries from Mars on Wednesday, November 3, in the Assembly Room of Winants Hall, Old Queens Campus, New Brunswick, NJ.

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THIRTY SEVENTH ANNUAL

OPEN HOUSE...

SATURDAY, JANUARY 29

A RADICAL NEW VIEW OF PREHISTORY:

Who were the first humans to populate North America?

Dr. Dennis Stanford United States National Museum Smithsonian Institution Department of Anthropology

VOLCANISM IN CENTRAL AMERICA:

Volcanoes, Sediments, and Subduction

Dr. Michael Carr Rutgers University Dept. of Geological Sciences New Brunswick, NJ

AND MORE...

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Mars: The latest discoveries

The rovers were designed to examine

Mars for evidence of water, to gather information about the Martian climate, to expand knowledge about the planet’s geology, and finally to prepare for the direct exploration of Mars by humans. Behind all of that is the central question of whether or not there is or ever was life on Mars.

The presence of liquid water on

Mars, either in the ancient past or preserved in the subsurface today, is central to the question of life because of water’s close association with life on Earth. If Mars once had liquid water, did life develop? Is there any indication of life in the planet’s past? Do any of these organisms still exist?

The minerals of the planet’s

surface hold clues because some minerals require liquid water to form. If present on the Martian surface, they would confirm the presence of liquid water. Carbonate and clay minerals are of special interest because their formation is closely associated with water.

Each rover has three sensors to identify the mineral and chemical content of Martian rocks. The alpha particle x-ray spectrometer can determine the elemental content of Martian rocks from the radiation they emit. Those elements are clues about the formation of the planet’s crust, and evidence about weathering on its surface.

The Mini-Thermal Emission

Spectrometer can identify minerals at a distance. All warm objects emit heat, but different objects emit heat differently. The spectra of emissions can indicate the species of minerals present and their relative abundance.

The Mossbauer spectrometer uses

gamma-rays and is most effective in detecting the abundance and composition of iron rich minerals. Gamma-rays are a high-energy electromagnetic radiation and they overlap the most energetic part of the x-ray spectrum.

To help the sensors make valid readings, the rover is also equipped with a rock abrasion tool. It prepares fresh surfaces for the other instruments to examine. All of the rover’s equipment must be able to operate in extreme conditions, like temperatures of –148oC (-208o F) to successfully gather information.

In addition to the spectrometers,

the landers are equipped with a panoramic stereo camera for imaging their environs. The images of the landing area are equal in importance to the geologic and historical data because they help prepare for the next mission.

“The successful landings of Spirit

and Opportunity give us the chance to see how information from the Mars orbiter correlates with conditions on the surface,” said Dr. Golombek. “That will be critical in picking future landing sites.”

A Radical New View of Prehistory: Who were the first humans to populate North America?

A radical new hypothesis of North American prehistory, promoted by Dr. Dennis Stanford of the Smithsonian Institution’s Department of Anthropology, proposes that North America’s first inhabitants were from the region of the Iberian Peninsula.

It has long been thought that the continent’s first settlers came from Asia across a land bridge, made their way into Alaska, and found an ice-free “highway” down into the continent about 13,500 years ago. Their culture has been found in excavations across North America. They had distinctive weapons and are named Clovis after Clovis, New Mexico where their artifacts were first discovered around 1929.

The new hypothesis considers the possibility that the earliest inhabitants of North America were a maritime adapted Paleolithic people. They may have hunted along the edge of the North Atlantic ice shelf that connected Europe with North America slightly more than 18,000 years ago. These people, known as Solutreans,

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originally inhabited the Iberian Peninsula. They manufactured both flint and bone tools that are nearly indistinguishable from those made by the Clovis people of North America.

Dr. Stanford suggests that these Paleolithic explorers originally settled along the U.S. eastern seaboard. Their hunting and gathering culture then spread to the North American deserts, the Canadian tundra, and perhaps into South America during the next six thousand years.

“Although the Solutreans may not have been the only ‘paleo-explorers’ to reach the Western Hemisphere,” said Dr. Stanford, “there are very few Clovis cultural traits that are not found in Solutrean sites. Many of their tools and cultural features are virtually indistinguishable, so much so, that if Clovis artifacts were found in a Spanish Solutrean site, archaeologists would not raise an eyebrow.”

Those similarities and the lack of Clovis-style implements from eastern Siberia, the usual locality suggested for the origin of the Clovis culture, support Dr. Stanford’s position.

Other scientists point out that the Solutrean hypothesis is such a radical departure that it might take years to properly evaluate. They also point out that no unequivocal Solutrean settlement remains have been found in North America. The new explanation, they note, is based primarily on comparisons of cultural traits along with artifacts already discovered on both sides of the Atlantic.

“These radical new ideas may be off the wall, but they will sink or swim on the basis of the evidence,” said Dr. Stanford. “Right now, the artifacts favor the Solutrean hypothesis.”

DNA analysis provides another possible linkage. Studies of mitochondrial DNA, sometimes called the Eve Gene, have isolated a haplogroup (having half the number of chromosomes in a normal cell) known as X. This haplogroup is occasionally found among Iberian and North American populations, and is

most often present in the native tribes of Northeastern North America. Moreover, the X haplogroup does not occur in eastern Siberia.

“Populations with the haplogroup X

marker have been identified in a large number of pre-Columbian burials,” said Dr. Stanford. “That suggests the possibility that it was present in the New World between 12,000-21,000 years ago. Perhaps the population that carried this genetic marker from Europe to the Americas was indeed the Solutrean people,” he said.

Volcanism in Central America: volcanoes, sediments, and subduction

“Central America is a fabulous place for volcanologists,” said Dr. Michael Carr of the Rutgers University Department of Geological Sciences. “It has one of the highest densities of active volcanoes in the world. It is also easier to get to than most other volcanic areas and it has an agreeable climate.”

“The first excellent characteristic of Central American volcanoes is that their magmas (melted rocks) are minimally contaminated as they rise through the relatively young and thin continental crust,” Carr said. “The lack of contamination gives geologists a clear window through which to identify the sources of the magma, to understand what happens in subduction zones, and to refine plate tectonics.”

The geologic setting of volcanoes

can be understood in terms of plate tectonics. The crust of the earth is a mosaic of continental and oceanic plates. In Central America, oceanic and continental plates are colliding.

The oceanic plate is less buoyant

than the continental plate because it is richer in heavy elements. Because of its density, the oceanic plate subducts, or sinks, beneath the continental plate.

The oceanic plate is also more dense

than the mantle, the layer of rock beneath the Earth’s crust. They are nearly identical in composition but

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the mantle is much hotter and therefore expanded.

The oceanic plate is covered with a very thin layer of sediment. During subduction, the sinking plate is heated by friction and conduction from the surrounding hot mantle. Increasing heat and pressure cause chemical reactions in the sediment and oceanic crust. Those reactions lead to the release of water and possibly some melting, primarily of the sediments.

The fluids generated during subduction migrate into the adjacent mantle and trigger more melting. The newly formed magma is less dense than its surroundings and buoyantly rises to the surface, where it erupts.

The trace element chemistry of lava is strongly influenced by the sediments on the subducted crust. “Sediments ‘fingerprint’ the chemistry of the lava. Each element has its ‘trick’ or story depending on where it is in the sedimentary rock column,” said Dr. Carr.

“Beryllium ten (10Be), for example, is an element formed by the bombardment of cosmic rays and has a half-life of about 2.5 million years. Because it is created near the Earth’s surface and has a short half-life, 10Be is restricted to the top 100 meters of sediments. If a lava is rich in 10Be, we can conclude that the top layer of sediment was not scraped off as the oceanic plate plunged beneath the continent. Furthermore, the entire process of subduction, melt generation and eruption must have happened in less than 5 million years.” he said.

“Most of my present research is

collecting the chemical evidence,” said Dr. Carr. “There are more than 40 volcanic centers in Central America to analyze and hundreds of individual vents. That is a wonderfully large sample.”

“As the quality and scope of the

data have increased over the 35 years I have been working in Central America, we have generated and tested many hypotheses about the processes of subduction and magma generation. We now have a robust basic model for

Central American magmatism and many unresolved questions. Finding clever ways to resolve basic questions is a satisfying part of doing science,” he said.

Pacaya volcano in Guatemala has been erupting continuously and sometimes violently since 1963. This type of volcanic activity is called Strombolian after the volcano in Italy that erupts in the same manner.

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