Tuesday, June 30, 2009

NASA, Japan Release Most Complete Topographic Map of Earth.

WASHINGTON -- NASA and Japan released a new digital topographic map of Earth Monday that covers more of our planet than ever before. The map was produced with detailed measurements from NASA's Terra spacecraft. The new global digital elevation model of Earth was created from nearly 1.3 million individual stereo-pair images collected by the Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer, or ASTER, instrument aboard Terra. NASA and Japan's Ministry of Economy, Trade and Industry, known as METI, developed the data set. It is available online to users everywhere at no cost. "This is the most complete, consistent global digital elevation data yet made available to the world," said Woody Turner, ASTER program scientist at NASA Headquarters in Washington. "This unique global set of data will serve users and researchers from a wide array of disciplines that need elevation and terrain information." According to Mike Abrams, ASTER science team leader at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the new topographic information will be of value throughout the Earth sciences and has many practical applications. "ASTER's accurate topographic data will be used for engineering, energy exploration, conserving natural resources, environmental management, public works design, firefighting, recreation, geology and city planning, to name just a few areas," Abrams said. Previously, the most complete topographic set of data publicly available was from NASA's Shuttle Radar Topography Mission. That mission mapped 80 percent of Earth's landmass, between 60 degrees north latitude and 57 degrees south. The new ASTER data expands coverage to 99 percent, from 83 degrees north latitude and 83 degrees south. Each elevation measurement point in the new data is 98 feet apart. The ASTER data fill in many of the voids in the shuttle mission's data, such as in very steep terrains and in some deserts," said Michael Kobrick, Shuttle Radar Topography Mission project scientist at the Jet Propulsion Laboratory. "NASA is working to combine the ASTER data with that of the Shuttle Radar Topography Mission and other sources to produce an even better global topographic map." NASA and METI are jointly contributing the ASTER topographic data to the Group on Earth Observations, an international partnership headquartered at the World Meteorological Organization in Geneva, Switzerland, for use in its Global Earth Observation System of Systems. This "system of systems" is a collaborative, international effort to share and integrate Earth observation data from many different instruments and systems to help monitor and forecast global environmental changes. NASA, METI and the U.S. Geological Survey validated the data, with support from the U.S. National Geospatial-Intelligence Agency and other collaborators. The data will be distributed by NASA's Land Processes Distributed Active Archive Center at the U.S. Geological Survey's Earth Resources Observation and Science Data Center in Sioux Falls, S.D., and by METI's Earth Remote Sensing Data Analysis Center in Tokyo. ASTER is one of five Earth-observing instruments launched on Terra in December 1999. ASTER acquires images from the visible to the thermal infrared wavelength region, with spatial resolutions ranging from about 50 to 300 feet. A joint science team from the U.S. and Japan validates and calibrates the instrument and data products. The U.S. science team is located at NASA's Jet Propulsion Laboratory.

Death Valley

Death Valley, Calif., has the lowest point in North America, Badwater at 85.5 meters (282 feet) below sea level. It is also the driest and hottest location in North America. Located in eastern California and western Nevada, Death Valley forms part of Death Valley National Park. The region is characterized by deep valleys and high mountain ranges, located in the large Basin and Range province of the western United States. This view looking towards the northwest was created by draping an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) simulated natural color image over digital topography from the ASTER Global Digital Elevation Model (GDEM) data set. Furnace Creek ranch in the right foreground is the only place on the valley floor where vegetation grows year-round due to water channeled through Furnace Creek. The ASTER scene was acquired September 24, 2003, and is located near 36.4 degrees north latitude, 116.9 degrees west longitude.

Himalayan glaciers in Bhutan

In the Bhutan Himalayas, Advanced Spaceborne Thermal Emission and Reflection Radiometer data have revealed significant spatial variability in glacier flow, such that the glacier velocities in the end zones on the south side exhibit significantly lower velocities (9 to 18 meters, or 30 to 60 feet per year), versus much higher flow velocities on the north side (18 to 183 meters, or 60 to 600 feet per year). The higher velocity for the northern glaciers suggests that the southern glaciers have substantially stagnated ice. This view looking towards the northwest was created by draping an ASTER simulated natural color image over digital topography from the ASTER Global Digital Elevation Model (GDEM) data set. The ASTER scene was acquired November 20, 2001, and is centered near 28.3 degrees north latitude, 90.1 degrees east longitude.

Source of the article and photographs:


Friday, June 26, 2009

Striking view of Sarychev volcano (Russia’s Kuril Islands, northeast of Japan).

A fortuitous orbit of the International Space Station allowed the astronauts this striking view of Sarychev volcano (Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Sarychev Peak is one of the most active volcanoes in the Kuril Island chain and is located on the northwestern end of Matua Island. Prior to June 12, the last explosive eruption had occurred in 1989 with eruptions in 1986, 1976, 1954 and 1946 also producing lava flows. Commercial airline flights were diverted from the region to minimize the danger of engine failures from ash intake. This detailed photograph is exciting to volcanologists because it captures several phenomena that occur during the earliest stages of an explosive volcanic eruption. The main column is one of a series of plumes that rose above Matua Island (48.1 degrees north latitude and 153.2 degrees east longitude) on June 12. The plume appears to be a combination of brown ash and white steam. The vigorously rising plume gives the steam a bubble-like appearance; the surrounding atmosphere has been shoved up by the shock wave of the eruption. The smooth white cloud on top may be water condensation that resulted from rapid rising and cooling of the air mass above the ash column, and is probably a transient feature (the eruption plume is starting to punch through). The structure also indicates that little to no shearing winds were present at the time to disrupt the plume. By contrast, a cloud of denser, gray ash -- most probably a pyroclastic flow -- appears to be hugging the ground, descending from the volcano summit. The rising eruption plume casts a shadow to the northwest of the island (bottom center). Brown ash at a lower altitude of the atmosphere spreads out above the ground at upper right. Low-level stratus clouds approach Matua Island from the east, wrapping around the lower slopes of the volcano. Only about 1.5 kilometers of the coastline of Matua Island (upper center) can be seen beneath the clouds and ash.
Image Credit: NASA

Tuesday, June 9, 2009

Erosional features on the top of the hill near Ranchi city of India.

Evidence of lost river is also seen.
Dr. Nitish Priyadarshi

Few days ago one of my friend from National TV News channel requested me to accompany him to the hill which is 20 kms south of Ranchi city in Jharkhand State of India. His purpose was to do a story on Hindu Mythology which is related to that hill. It was about the saint Valmiki who wrote Ramayana. According to the belief Valmiki stayed here. Interestingly the name of the hill is MARASREE. If you read it in hindi from opposite direction it will spell SHREERAM (name of the lord Rama of Ayodhya).

But my interest was not related to such findings. As being a geologist I was more interested on the geological aspect of the area. After climbing on the top of the hill I saw different geological erosion and weathering. This hill is dome shaped popularly known as dome –gneiss. This low gentle dome like feature is a residual phenomenon and in this ancient part of the crust it represents the end stage of the degradation of a higher hill. Such a dome –gneiss, however, is due to the highly massive non-fractured and non-jointed nature of the mass.

There is one small water pond and different potholes, and small circular depressions on the top. Probable source of water to this pond and other potholes is from inside the hill. In the rocky beds of streams we have kettle-like depressions, called potholes. They may be seen both in long and cross profiles. The stream beds in Jharkhand Plateaus are frequently dotted with potholes. A pothole is formed by the constant swirl of an eddy, which carries pebbles or sand round and round in one spot. Gradually a hole is bored downward into the rock. The sand and pebbles that served as the tools may often be found at the bottom of the depression. Whether the vortex be one in a current of wind or water or ice, the action is the same, although the rate of abrasion may vary. Potholes are most commonly of fluviatile origin. So presence of potholes on the top of the hill clearly indicates that water used to flow in geological past.

Writer found a shallow valley eroding the hill from the top of the hill to the base. From the satellite image evidence of abandoned flow path of water in form of different rivulets in the valley are seen. It may also be the evidence of the flow path of the lost river. In earlier days water filled in the pond on the top of the hill may have been the regular source of water to this river. Pond still exist on the top but river has vanished or it may be flowing only in rainy season. Depletion of groundwater level due to extreme long heat season in Ranchi plateau is affecting such rivers which are dependent only on groundwater flow. Many such small rivers originating from the top of the hills in Jharkhand state has now dried up or flow only during rainy season.

Pond water of the studied hill is highly polluted which is evident with its green colour. pH value is 12.

Many stone minings are going around this hill posing threat to this hill. State government should take care to preserve such hills which has kept the evidences of earlier geological history of more than 2 billion years.

Friday, June 5, 2009

The evolution of the earth’s early atmosphere.

How did Earth's early atmosphere evolved.
Dr. Nitish Priyadarshi

The Earth's atmosphere (or air) is a layer of gases surrounding the planet Earth that is retained by the Earth's gravity. It has a mass of about five quadrillion metric tons. Dry air contains roughly (by volume) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, and trace amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night.

The solid earth accumulated about 4700 m.y. ago from a cloud of cosmic particles and gaseous materials and as they collected gravitationally a hot planetary nucleus formed. This nucleus eventually became the present core as the mantle and crust consolidated. An atmosphere probably existed even in these early stages of the first billion years of earth’s history, though it was apparently transitory. Judging from the atmospheres of the major planets, Jupiter and Saturn, which retain light elements by virtue of their large gravitational attraction, hydrogen and helium would have been abundant in earth’s primordial atmosphere. These elements were derived in part from the original gaseous material of the cosmic cloud, but volcanic outgassing during lithification of the crust probably continued as well. Neon and argon and some of the lighter gases such as xenon probably also existed in the early atmosphere.

The first atmosphere of the earth, then, contained hydrogen, helium, neon, argon and various other lighter and inert gases, none of which is abundant in the present atmosphere. Most of these on liberation to the air now either escape earth’s gravitational pull because of their low densities or are bound up in minerals by chemically reacting with them. It is likely that the primitive atmosphere did not linger long but was dissipated through these processes.

A little reflection tells us that earth’s present atmosphere necessarily evolved from one that was different. We know no primary source for the free molecular oxygen that comprises one –fifth of our present atmosphere. Compared with solar abundances, our atmosphere has only traces of hydrogen and helium but a disproportionate amount of nitrogen.

An important clue to the origin of our ancestral atmosphere is found in the abundances of so-called noble gases – elements that, unlike oxygen, do not (or rarely) combine with others because they have the stable configuration of 8 (or 2 in the case of helium) in their outermost shell of electrons. As they do not ordinarily lose, gain, or share electrons with other elements, variations in their abundance imply different sources. Had earth inherited its atmosphere directly from the solar nebula, the gaseous elements neon, argon, krypton, xenon, and radon should be present in approximately solar abundances, allowing for the addition of radiogenic isotopes. That is not the case. It has been repeatedly noted over the past half-century that all the noble gases are grossly depleted in the earth’s atmosphere compared with solar and cosmic abundances. They are depleted, in fact, by several to many orders of magnitude. This means either that earth accumulated without an atmosphere of nebular proportions or that any initial atmosphere escaped its gravity field in some subsequent episode of heating that accelerated even the heavy noble gases to escape velocities.

The most significant development following sufficient cooling and consolidation of the surface rocks was liberation of abundant water along with CO2 , N2, and H2 S by volcanic outgassing. Water vapor is dissociated in the upper atmosphere by ultraviolet light to yield oxygen and hydrogen. This process constituted the sole source of free oxygen of the early atmosphere, and the build up to significant oxygen concentrations occupied the long interval between at least 3400 and about 2000 m.y. ago. Further, oxygen of the early high atmosphere was photochemically converted to ozone as at present, and with time, ozone concentration led to the development of a screen to ultraviolet light. Lastly, accumulation of water molecules in the atmosphere caused extensive precipitation and hence the initiation of the oceans at some time prior to 3760 m.y. ago, when the oldest known sedimentary rocks were deposited.

Other concept regarding evolution of early oxygen in atmosphere:
If earth’s primitive atmosphere resulted from volcanic outgassing, we have a problem, because volcanoes do not emit free oxygen. Where did the very significant percentage of oxygen in our present atmosphere (20 percent) come from?

The major source of oxygen is green plants. Plants did not just adapt to their environment, they actually influenced it, dramatically altering the composition of the entire planet’s atmosphere by using carbon dioxide and releasing oxygen. This is a good example of how earth operates as a giant system in which living things interact with their environment.

How did plants come to alter the atmosphere? The key is the way in which plants create their own food. They employ photosynthesis, in which they use light energy to synthesize food sugars from carbon dioxide and water. The process releases a waste gas, oxygen. Those of us in the animal kingdom rely on oxygen to metabolize our food, and we in turn exhale carbon dioxide as a waste gas. The plant use this carbon dioxide for more photosynthesis, and so on, in a continuing system.

The first life-forms on earth, probably bacteria, did not need oxygen. Their life processes were geared to the earlier, oxygen less atmosphere. Even today, many anaerobic thrive in environments that lack free oxygen. Later, primitive plants evolved that used photosynthesis and released oxygen. Slowly, the oxygen content of earth’s atmosphere increased. The Precambrian rock record suggests that much of the first free oxygen did not remain free because it combined with (oxidized) other substances dissolved in water, especially iron. Iron has tremendous affinity for oxygen, and the two elements combine to form iron oxides (rust) at any opportunity. To this day, the majority of oxygen produced over time is locked up in the ancient "banded rock" and "red bed" formations.

Then, once the available iron satisfied its need for oxygen, substantial quantities of oxygen accumulated in the atmosphere. By the beginning of the Paleozoic era, about 4 billion years into earth’s existence, the fossil record reveals abundant ocean- dwelling organisms that require oxygen to live.
Once oxygen had been produced, ultraviolet light split the molecules, producing the ozone UV shield as a by-product. Only at this point did life move out of the oceans and respiration evolved.
Hence, the composition of earth’s atmosphere has evolved together with its life-forms, from an oxygen less envelop to today’s oxygen-rich environment.

Cloud,P. 1988. Oasis in space, earth history from the beginning. W.W. Norton & Company, New York.
Frakes, L. A. 1979. Climates throughout geologic times. Elsevier, New York.
Tarbuck, E.J. and Lutgens, F.K. 1994. Earth Science. Prentice Hall, New Jersey.

Thursday, June 4, 2009

Anatomy of a Busted Comet

NASA's Spitzer Space Telescope captured this image of comet Holmes in March 2008, five months after the comet suddenly erupted and brightened a millionfold overnight. Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the asteroid belt.
Image Credit: NASA/JPL-Caltech