Thursday, February 25, 2010

SIGNS OF LIQUID WATER IN SATURNIAN MOON

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Scientists working on the Cassini space mission have found negatively charged water ions in the ice plume of Enceladus. Their findings, based on analysis from data taken in plume fly-throughs in 2008 and reported in the journal Icarus, provide evidence for the presence of liquid water, which suggests the ingredients for life inside the icy moon. The Cassini plasma spectrometer, used to gather this data, also found other species of negatively charged ions including hydrocarbons.

“While it’s no surprise that there is water there, these short-lived ions are extra evidence for sub-surface water and where there’s water, carbon and energy, some of the major ingredients for life are present,” said lead author Andrew Coates from University College London’s Mullard Space Science Laboratory.

“The surprise for us was to look at the mass of these ions. There were several peaks in the spectrum, and when we analysed them we saw the effect of water molecules clustering together one after the other.” The measurements were made as Cassini plunged through Enceladus’ plume on March 12, 2008.

Enceladus thus joins Earth, Titan and comets where negatively charged ions are known to exist in the solar system. Negative oxygen ions were discovered in Earth’s ionosphere at the dawn of the space age. At Earth’s surface, negative water ions are present where liquid water is in motion, such as waterfalls or crashing ocean waves.

The Cassini plasma spectrometer, originally designed to take data in Saturn’s magnetic environment, measures the density, flow velocity and temperature of ions and electrons that enter the instrument. But since the discovery of Enceladus’ water ice plume, the instrument has also successfully captured and analysed samples of material in the jets.

Early in its mission, Cassini discovered the plume that fountains water vapour and ice particles above Enceladus. Since then, scientists have found that these water products dominate Saturn’s magnetic environment and create Saturn’s huge E-ring.

At Titan, the same instrument detected extremely large negative hydrocarbon ions with masses up to 13,800 times that of hydrogen. A paper in Planetary and Space Science by Coates and colleagues in December 2009 showed that, at Titan, the largest hydrocarbon or nitrile ions are seen at the lowest altitudes of the atmosphere that Cassini flew (950 kilometers (590 miles). They suggest these large ions are the source of the smog-like haze that blocks most of Titan’s surface from view. They may be representative of the organic mix called “tholins” by Carl Sagan when he produced the reddish brew of prebiotic chemicals in the lab from gases that were known to be present in Titan’s atmosphere. Tholins that may be produced in Titan’s atmosphere could fall to the moon’s surface and may even make up the sand grains of the dunes that dominate part of Titan’s equatorial region.

The new findings add to our growing knowledge about the detailed chemistry of Enceladus’ plume and Titan’s atmosphere, giving new understanding of environments beyond Earth where prebiotic or life-sustaining environments might exist.

(Photo: NASA)

Science & Technology Facilities Council

RICE PHYSICISTS KILL CANCER WITH 'NANOBUBBLES'

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Using lasers and nanoparticles, scientists at Rice University have discovered a new technique for singling out individual diseased cells and destroying them with tiny explosions. The scientists used lasers to make "nanobubbles" by zapping gold nanoparticles inside cells. In tests on cancer cells, they found they could tune the lasers to create either small, bright bubbles that were visible but harmless or large bubbles that burst the cells.

"Single-cell targeting is one of the most touted advantages of nanomedicine, and our approach delivers on that promise with a localized effect inside an individual cell," said Rice physicist Dmitri Lapotko, the lead researcher on the project. "The idea is to spot and treat unhealthy cells early, before a disease progresses to the point of making people extremely ill."

The research is available online in the journal Nanotechnology.

Nanobubbles are created when gold nanoparticles are struck by short laser pulses. The short-lived bubbles are very bright and can be made smaller or larger by varying the power of the laser. Because they are visible under a microscope, nanobubbles can be used to either diagnose sick cells or to track the explosions that are destroying them.

In laboratory studies published last year, Lapotko and colleagues at the Laboratory for Laser Cytotechnologies at the A.V. Lykov Heat and Mass Transfer Institute in Minsk, Belarus, applied nanobubbles to arterial plaque. They found that they could blast right through the deposits that block arteries.

"The bubbles work like a jackhammer," Lapotko said.

In the current study, Lapotko and Rice colleague Jason Hafner, associate professor of physics and astronomy and of chemistry, tested the approach on leukemia cells and cells from head and neck cancers. They attached antibodies to the nanoparticles so they would target only the cancer cells, and they found the technique was effective at locating and killing the cancer cells.

Lapotko said the nanobubble technology could be used for "theranostics," a single process that combines diagnosis and therapy. In addition, because the cell-bursting nanobubbles also show up on microscopes in real time, Lapotko said the technique can be used for post-therapeutic assessment, or what physicians often refer to as "guidance."

Hafner said, "The mechanical and optical properties of the bubbles offer unique advantages in localizing the biomedical applications to the individual cell level, or perhaps even to work within cells."

Rice University

HOW ALGAE MASTERED QUANTUM PHYSICS

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Simple single-celled algae use highly sophisticated quantum physics to harvest and convert solar energy for their survival, a new study suggests.

The study, published in the prestigious science journal Nature, was by an international team of Canadian, Italian and Australian researchers, including two UNSW biophysicists – Professor Paul Curmi and Dr Krystyna Wilk.

It sheds new light on the process of photosynthesis used by green plants and algae to harvest energy from the sun. The findings may open up new avenues to develop organic solar cells and other electronic devices that emit or are initiated by light, such as lasers and visual displays.

The water-dwelling algae are in effect highly miniaturised quantum computers, the study suggests. They have mastered the process of photosynthesis so well that they can convert sunlight into electrical energy with near-perfect efficiency.

They do so by having their light-harvesting proteins "wired" together through a phenomenon known as quantum coherence, enabling them to transfer energy from one protein to another with lightning-fast speed and so reduce energy loss along the energy conversion pathway.

The study is part of a larger, ongoing collaboration between the biophysics lab at the UNSW School of Physics, the Centre for Applied Medical Research, St Vincent's Hospital Sydney, and the University of Toronto.

"We are working on understanding how a group of single-celled algae can thrive under low light conditions in marine and freshwater habitats,' Professor Curmi said.

"To do this, they must be incredibly efficient in capturing all solar energy and converting it to chemical energy via photosynthesis. They cannot afford to let any solar energy escape, so they have evolved elaborate antenna systems that trap light.”

(Photo: UNSW)

The University of New South Wales

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