SETI bioastro: Bishun Khare Laid Groundwork For Current Cassini Mission

• Previous message: LARRY KLAES: "SETI bioastro: Fw: Cassini close ups of Titan thrill, mystify scientists"

Bishun Khare Laid Groundwork For Current Cassini Mission by: Francis C. Assisi<http://www.indolink.com/feedback.php?Recipient=Francis&ColumnName=SciTech&Subject=Bishun Khare Laid Groundwork For Current Cassini Mission>

--------------------------------------------------------------------------------

Boston, 4 July -- Last week, after a nearly seven-year journey covering 3.5 billion kilometers, the international Cassini-Huygens mission began an extensive probe into deep space.
With its highly sophisticated science instruments the Cassini mission's four-year study will include Saturn´s rings, icy satellites, magnetosphere and Titan, the planet's largest moon. The $3 billion mission represents the best technical efforts of 260 scientists from the United States and 17 European nations.

The study of Titan is one of the major goals of the mission. That's because scientists believe that Titan may preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth. "Titan is like a time machine taking us to the past to see what Earth might have been like," said Dr. Dennis Matson, Cassini project scientist at NASA´s Jet Propulsion Laboratory, Pasadena, Calif. "The hazy moon may hold clues to how the primitive Earth evolved into a life-bearing planet."

Titan appears to be one of the few places in the solar system with a substantial atmosphere -- composed largely of nitrogen and methane gas. It features fluids that hint of a chemistry on Titan close to what is needed for biological activity. Scientists believe that Titan´s hydrocarbon environment may emulate, at least in part, "the kind of chemistry that Earth had 4 billion years ago" in the "pre-biotic" years before life evolved. That's because the kinds of chemistry at work on Titan today resembles the ones at work on the Earth 4 billion years ago, before there was life. Therefore exploring Titan is like exploring the Earth´s pre-biotic past.

"Titan is like a time machine taking us to the past to see what Earth might have been like," said Dr. Dennis Matson, Cassini project scientist at NASA´s Jet Propulsion Laboratory, Pasadena, Calif. "The hazy moon may hold clues to how the primitive Earth evolved into a life-bearing planet."

Explains Dr. Ed Weiler, associate administrator for space science at NASA Headquarters, Washington, D.C.: "The Saturn system represents an unsurpassed laboratory, where we can look for answers to many fundamental questions about the physics, chemistry and evolution of the planets and the conditions that give rise to life," he said.

Professor Ian Halliday, chief executive of the Particle Physics and Astronomy Research Council, agrees: "Saturn is hailed as the 'jewel' of the Solar System. It has fascinated us for centuries. Right now we stand on the threshold of a wealth of scientific discovery as we unveil Saturn's secrets. The more we can learn about the planet and indeed Titan, then we can better understand our own place in the universe."

INDIAN AMERICAN SCIENTIST DR. BISHUN KHARE

That's why for nearly thirty years, first with Carl Sagan at the Laboratory for Planetary Studies at Cornell University, and now at NASA's Ames Research Center and the SETI (Search For Extraterrestrial Intelligence) team based in Mountain View, Indian American scientist Dr. Bishun N. Khare has been doing just that - exploring Titan with a passion.

In the process, Khare has laid an extraordinary foundation for Cassini's probe of our solar system's Saturn and its moon Titan.

With Sagan, Khare studied Polycyclic aromatic hydrocarbons in the atmospheres of Titan and Jupiter and reported that they were important components of the interstellar medium.

Khare was among the first to conduct laboratory simulation of Titan's atmosphere composed of nitrogen, carbon dioxide, and methane. He was responsible for the tantalizing discovery of Tholins, the brown complex organics precipitating from Titan´s stratospheric aerosol layers and suggested that it may be part of important surface chemistry leading to the next step toward life. "Tholin" is a term coined by Carl Sagan (from the Greek "tholos," meaning mud). Today, as scientists prepare for Cassini's activities over the next four years, the search for evidence of intelligent life on other planets -- along with the mainstream quest of answering more precisely how the universe came to be, what it´s made of and where it may be headed will receive additional boost and will be set firmly on the experimental foundation built over the years by Khare.

Khare's revolutionary finding, through simulations of Titan´s atmosphere, is that the smoggy hydrocarbon haze that contains molecules called tholins that can form the foundations of the building blocks of life. For example, amino acids, one of the building blocks of terrestrial life, form when these red-brown smog-like particles are placed in water.

When Khare and colleagues analyzed the building blocks of tholins by pyrrolysis, splitting up the tholins using plasma, the scientists found a rich array of biomolecular building blocks such as pyrroles, pyrazines, pyridines and pyrimidines. All of these molecules have played an important role in the evolution of life.

Most coenzymes (molecules that are indispensable in powering biological metabolism) and vitamins contain a central heterocyclic ring (a ring composed of several hexagons or pentagons of carbon atoms), which is necessary to fulfill the biological function of the coenzyme. This observation has spawned the idea that coenzymes were formed early in the history of life and may have been present during the period of terrestrial evolution where life was about to begin.

Could they have originated as a product of atmospheric gas phase chemistry in the nitrogen rich atmosphere of early Earth?

This is a question that Sagan, Khare and many of their colleagues asked themselves nearly three decades ago. As they pointed out, Titan may be regarded as a broad parallel to the early terrestrial atmosphere with respect to its chemistry and in this way, it is certainly relevant to the origins of life.

Acknowledges Emma Bakes of SETI: "Building on the work of Sagan, Khare and their colleagues, we will investigate the importance of a hydrocarbon haze in accelerating the conditions necessary for life and the large molecules involved in its metabolism. A better idea of how life formed on Earth and how the transition was made from chemistry to biochemistry can be obtained by compressing thousands to millions of years of chemistry into one run of a computer model. "

Scientists have also suspected that organic solids have been falling from Titan´s sky for billions of years and might be compounds that set the stage for the next chemical step toward life. Khare was able to create compounds like those condensing from Titan´s sky by bombarding an analog of Titan´s atmosphere with electrons. This produces "tholins" -- organic polymers (plastics) found in Titan´s upper nitrogen-methane atmosphere.

Titan´s tholins are created by ultraviolet sunlight and electrons streaming out from Saturn´s magnetic field. Tholins must dissolve to produce amino acids that are the basic building blocks of life. But chemists know that tholins won´t dissolve in Titan´s ethane/methane lakes or oceans. However, they readily dissolve in water or ammonia. And experiments done 20 years ago show that dissolving tholins in liquid water produces amino acids. So given liquid water, there may be amino acids brewing in Titan´s version of primordial soup.

Oxygen is the other essential for life on Earth. But there is almost no oxygen in Titan´s atmosphere. Last year, however, Caitlin Griffith, of University of Arizona's Lunar and Planetary Laboratory, discovered water ice on Titan´s surface. UA planetary scientist Jonathan Lunine and others theorize that when volcanoes erupt on Titan, some of this ice could melt and flow across the landscape. Similar flows could result when comets and asteroids slam into Titan.

Better still, Titan´s water may not immediately freeze because it´s probably laced with enough ammonia (antifreeze) to remain liquid for about 1,000 years, Smith and Lunine noted in a research paper published in last November´s issue of "Astrobiology."

So although Titan is extremely cold -- about 94 degrees kelvin (minus 180 degrees Celsius or minus 300 degrees Fahrenheit) -- water may briefly flow across the surface, supplying oxygen and a medium for chemistry, they conclude.

To further understand how all this might work together, Khare is generating tholins in the lab, analyzing their spectroscopic properties, and trying to understand their chemistry. Khare is trying to find out what sorts of molecules have evolved, and whether they´ve evolved along pathways that might provide insights into how biological molecules developed on primordial Earth.

Some of what Khare and colleagues have learned so far in their experiments is that these materials are gross mixtures of incredibly complex molecules. All this, as a result of evolution -- or time and energy input over billions of years.

That's why scientists involved with NASA´s Cassini Mission speculate that Titan´s thick orange aerosol haze layer, which Khare has shown to be basically a bunch of organic plastics -- polymers of carbon, hydrogen and nitrogen -- may eventually settle on Titan´s surface, where they produce the organic feedstock for any organic chemistry going on.

Cassini´s Huygens probe will be the first instrument to actually sample this aerosol. It will give scientists some rudimentary chemical information on this material. But the probe won´t tell them much about organic chemistry at Titan´s surface. A follow-up mission to Titan that includes a robotic organic chemistry laboratory is expected to give scientists a much more detailed look at the surface.

The Cassini spacecraft is scheduled to launch a probe into Titan´s atmosphere in December. This probe will float to Titan´s surface in January 2005.

As one scientist at NASA Astrobiology Institute explains: "We don´t really know how life formed on the Earth, or on whatever planet it formed, but Titan is our best chance to study organic chemistry in a planetary environment that has remained lifeless over billions of years."

This is where the pioneering work of Bishun N. Khare has laid the groundwork for Cassini's ongoing mission.

francisassisi_at_hotmail.com<mailto:francisassisi_at_hotmail.com>

• Previous message: LARRY KLAES: "SETI bioastro: Fw: Cassini close ups of Titan thrill, mystify scientists"

This archive was generated by hypermail 2.1.6 : Mon Jul 05 2004 - 07:55:34 PDT