LAMIS: A Green Chemistry Alternative for Remote-Controlled Laser Spectroscopy

LAMIS uses the energy of a high-powered laser beam to ablate a tiny spot on a sample, creating a plasma plume for spectroscopic analysis that reveals chemical elements and their isotopes. 

(Image courtesy of Applied Spectra, Inc.)

At some point this year, after NASA's rover Curiosity has landed on Mars, a laser will fire a beam of infrared light at a rock or soil sample.

This will "ablate" or vaporise a microgram-sized piece of the target, generating a plume of ionised gas or plasma, which will be analysed by spectrometers to identify the target's constituent elements.

Future Mars rovers, however, will be able to do even more. Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with Applied Spectra, Inc., have developed an advanced version of this laser technology that can also analyze a target's constituent isotopes.

This expanded capability will enable future rovers for the first time to precisely date the geological age of Martian samples.

From left, Alexander Bol'shakov, Xianglei Mao and Rick Russo are part of the research team that developed LAMIS, a green chemistry laser spectroscopy technology that can be operated across vast distances. (Photo by Roy Kaltschmidt, Berkeley Lab)

Rick Russo, a scientist with Berkeley Lab's Environmental Energy Technologies Division and a pioneer in laser ablation spectroscopy, led the development of LAMIS - for Laser Ablation Molecular Isotopic Spectrometry.

As with the earlier Laser Induced Breakdown Spectroscopy (LIBS) technology being used on rover Curiosity, the basic premise is to use the energy of a high-powered laser beam focused to a tiny spot on the surface of a sample to create a plasma plume for analysis.

Each species of atoms or ions within the plasma will emit light with signature spectral emission peaks.

However, whereas LIBS only measures the optical emission spectra of atoms and ions, LAMIS measures the emission spectra of molecules and molecular ions.

This enables LAMIS to identify the specific isotopes of a chemical element within the plasma plume.

"Relative to atomic emission, molecular spectra can exhibit significantly larger isotopic shifts due to the contributions of the vibrational and rotational motion in the molecule," Russo says.

"The trick is to be patient and wait for the hot atoms and ions in the plasma to collide and merge with the ambient environment to form an oxide, or a nitride or fluoride, and then collect the molecular light emissions."

Isotopes of Strontium
Russo and his research group have been using LAMIS to study isotopes of strontium, an alkaline earth metal commonly found in geological and natural materials.

Although strontium's major isotopes are stable (strontium-90 being a notable exception), the percentage of strontium-87 will naturally increase over time as a result of the decay of radioactive rubidium.

Comparing the ratio of strontium-87 to strontium-86 is a standard tool for age dating in geochronology, oceanography and archeology. The ratio of these strontium isotopes is also used to date the origin of historic or forensic samples.

Currently, the standard means of measuring strontium isotopic ratios is by mass spectrometry technologies that involve time-consuming, labour-intensive laboratory sample dissolution work with an extensive array of instrumentation.

This sample dissolution work generates substantial chemical waste. LAMIS offers a green chemistry alternative that is faster, less expensive and can be carried out from across vast distances.

"LAMIS is not yet as sensitive or precise as mass spectrometry but unlike mass spectrometry it does not require chemical dissolution sample preparation, vacuum chambers and a laboratory infrastructure," Russo says.

"All we need is a laser beam and an optical spectrometer and we can perform real-time isotopic analyses of samples at ambient pressures and temperatures."

LAMIS represents what may be the only practical means of determining the geochronology of samples on Mars or other celestial bodies in the Solar System.

Current age estimates of such bodies suffer from uncertainties in the billions of years. That said, LAMIS also has many important applications here on Earth.

Strontium isotope ratios have been a focus in the field of medicine for both treatment and diagnostic purposes.

NASA Chandra X-ray Image: Abell 2052 Galaxy Cluster Sloshes cosmic gas

Like wine in a glass, vast clouds of hot gas are sloshing back and forth in Abell 2052, a galaxy cluster located about 480 million light years from Earth.

X-ray data (blue) from NASA's Chandra X-ray Observatory shows the hot gas in this dynamic system, and optical data (gold) from the Very Large Telescope shows the galaxies.

The hot, X-ray bright gas has an average temperature of about 30 million degrees.

A huge spiral structure in the hot gas, spanning almost a million light years, is seen around the outside of the image, surrounding a giant elliptical galaxy at the center.

This spiral was created when a small cluster of galaxies smashed into a larger one that surrounds the central elliptical galaxy.

The smaller cluster passed the cluster core, the direction of motion of the cluster gas reversed and it travelled back towards the cluster centre.

The cluster gas moved through the centre again and "sloshed" back and forth, similar to wine sloshing in a glass that was jerked sideways.

The sloshing gas ended up in a spiral pattern because the collision between the two clusters was off-center.

The Chandra data show clear bubbles evacuated by material blasted away from the black hole, which are surrounded by dense, bright, cool rims.

As with the sloshing, this activity helps prevent cooling of the gas in the cluster's core, setting limits on the growth of the giant elliptical galaxy and its supermassive black hole.

Image Credit: X-ray: NASA/CXC/BU/L.Blanton; Optical: ESO/VLT

NASA Ultraviolet Optical telescope: Image of M31

This mosaic of M31 merges 330 individual images taken by the Ultraviolet/Optical Telescope aboard NASA's Swift spacecraft.

It is the highest-resolution image of the galaxy ever recorded in the ultraviolet.

Also known as the Andromeda Galaxy, M31 is more than 220,000 light-years across and lies 2.5 million light-years away.

On a clear, dark night, the galaxy is faintly visible as a misty patch to the naked eye.

The irregular shape of the image results when the more than 300 images were assembled to make the final image.

Image Credit: NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP)

Treatment of retinal conditions

“Retinal disease is highly prevalent among older individuals, and both age-related macular degeneration (AMD) and diabetic retinopathy account for more than half the irreversible blindness in older Americans. The prevalence of both macular degeneration and diabetic retinopathy increases with age, and the number of Americans affected by these conditions is expected to increase substantially as the number of Americans older than 65 years doubles from 2010 to 2040,” the authors write as background information in the article.

“The last decade has seen substantial changes in the treatment options available for many retinal diseases, particularly in the treatment of neovascular AMD,” a form of the disease involving abnormal blood vessel growth in the eye.

Pradeep Y. Ramulu, M.D., M.H.S., Ph.D., of Wilmer Eye Institute, Johns Hopkins University, Baltimore, and colleagues analyzed Medicare fee-for-service data claims filed between 1997 and 2007. Overall, the number of retinal procedures performed increased 192 percent. Increases occurred each year except between 1997 and 1998; the largest year-to-year increase in volume, 20 percent, occurred between 2006 and 2007.

“Procedure volumes changed most markedly for treatments directed toward neovascular AMD,” the authors write. New treatments for this condition include intravitreal therapy — injections of drugs administered directly into the eye — of antibodies that block the formation of new blood vessels. Between 1997 and 2001, fewer than 5,000 such injections were performed each year. However, rates more than doubled each year through 2006, increasing between 2001 (when 4,215 of these procedures were performed) and 2007 (when injections totaled 812,413).

Photodynamic therapy, a laser treatment for neovascular AMD approved in 2000, peaked in 2004 with 133,565 procedures and then decreased 83 percent to 22,675 procedures in 2007. Laser treatment of choroidal lesions (potentially cancerous eye tumors) and neovascular AMD also decreased 83 percent, from a peak of 82,089 in 1999 to 13,821 in 2007.

Vitrectomy — surgical removal of the gel inside the eye, used to treat retinal detachments — increased 72 percent, from 11,212 in 1997 to 19,923 in 2007. Scleral buckling, a treatment for the same condition involving placing a silicon buckle around the eye, can be performed with or without vitrectomy. Scleral buckling alone became less common during the study period (a 69 percent decrease, from 8,691 to 2,660).

“Observing use patterns adds value, because it demonstrates how disease is treated and can be used to identify possible discrepancies between the best evidence-based treatments for a condition (as defined by clinical trials and meta-analyses from the literature) and current practice patterns,” the authors conclude. “In this report, we observe that intravitreal injections of pharmacologic agents have gained widespread acceptance for the treatment of neovascular AMD and that vitrectomy is being increasingly applied to a wide range of retinal conditions.”

(Arch Ophthalmol. 2010;128[10]:1335-1340. Available pre-embargo to the media at www.jamamedia.org.)

Ultra-Precise Mirrors and Optical Systems For Space

Ultra-Precise Mirrors and Optical Systems For Space

Metal mirrors made with extremely high precision and exactly positioned are the key elements of modern telescopes.

A new production technique enables complex optical surfaces to be manufactured with excellent trueness of shape and hitherto unattained positional accuracy.

The mirrors have been built for an infrared sounder telescope.

For space research as well as climate observation and weather forecasting satellites need increasingly powerful optical measurement and recording devices.

They often consist of several aspherically shaped mirror elements which through their precise interplay provide the desired reflection of the incident light.

"All the mirrors must be produced and characterised with extreme precision, that is to an accuracy of less than one micrometer. They also have to be exactly positioned in relation to each other," explains Sebastian Scheiding from the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena. Up to now this positioning has been very time consuming as it takes place step by step.

First the individual mirrors are fitted in the telescope one after the other, then the imaging quality is measured.

If inaccuracies or errors are found, they are corrected by positional adjustments to the mirrors. Then further measurements and adjustments are made until all components are optimally arranged.

"We wanted to simplify this complicated and time-consuming adjustment process," says Scheiding. In the research project initiated by the German Aerospace Center (DLR) the scientist has therefore developed an innovative production technique which takes into account the later alignment of the components right from the outset.

For this purpose, the individual mirror surfaces are positioned in relation to each other as precisely during processing as they will be later in the telescope. This reduces to a minimum the errors and corrections made when the mirrors are being fitted. The assembly process is simple and reproducible.

"The trick is that we mount all the mirrors for a module in the same machine at the same time and assign them to a common system of coordinates.

To this end, each mirror blank is provided with defined, ultra-precise measurement marks and reference surfaces," explains Scheiding. These fixed marks embody the system of coordinates for diamond turning of the mirror shapes. At the same time, however, they fix the position of each mirror in relation to the adjacent mirrors. Finally they also serve as reference points for subsequent measurement processes to check the quality of the optical system.