Science 1663

Spotlight

Present at the Solar System’s Birth; Unusual Waves; Genie Pro; An MRI for Your Luggage

Present at the Solar System's Birth

Vesta and Ceres—two of the largest bodies in the main asteroid belt between the orbits of Mars and Jupiter—have remained largely intact since forming 4.5 billion years ago. These two asteroids essentially are records of the solar system's physical and chemical condition in its early planet-forming phase, which is why NASA's Dawn spacecraft is on its way to study them.

Tom Prettyman, in a clean suit, prepares GRaND (inset) for launch.

Launched in September, Dawn will reach Vesta and Ceres in August 2011 and May 2015, respectively. An onboard gamma-ray and neutron detector, GRaND, developed by Los Alamos, will then map the near-surface abundances of major rock-forming elements (oxygen, magnesium, aluminum, silicon, calcium, titanium, and iron). Combined with data from optical spectroscopy, the information will enable scientists to determine how the asteroids formed and evolved. The spectrometer will also map the abundance of hydrogen, which indicates the presence of ice or hydrated minerals. Lastly, GRaND will measure the abundances of the radioactive elements potassium, thorium, and uranium. The heat generated by the decay of these elements may have driven volcanic activity on Vesta or caused the formation of a sub-surface ocean on Ceres.

"GRaND will help us understand how the surfaces of Vesta and Ceres were shaped by such things as volcanism and the presence of water, giving us new insights into how the asteroids evolved," says Tom Prettyman, lead scientist for the Los Alamos instrument and co-investigator for Dawn.

GRaND can identify the major rock-forming elements because each emits a characteristic spectrum of gamma rays or neutrons when bombarded by galactic cosmic rays. It will similarly detect the gamma rays from the radioactive elements. Elemental abundances are determined by analyzing the gamma rays, with the neutrons providing additional but necessary information.

Unusual Waves

Forget Superman and "faster than a speeding bullet." How about superluminal and faster than the speed of light!

A superluminal transmitter.

John Singleton of Los Alamos and his collaborators have built a radio transmitter that incorporates a radio wave source that moves superluminally (faster than light). The emitted waves have several unusual properties. For example, they lose much less power over a distance than do ordinary radio waves; thus, they show promise for long-distance, low-power broadcasting applications.

Ordinary objects can't move faster than light. But consider a line of people where the first person snaps their fingers, then after a delay, the second person snaps theirs, and so on. The "snap" moves down the line with a speed determined by the delay, which can be arbitrarily short. Hence the snap can move arbitrarily fast.

The radio wave source moves similarly through the transmitter, a long, curved piece of dielectric (a material that can be polarized) with electric amplifiers attached every few inches. When triggered, the first amplifier "snaps its fingers" and produces a strong electric field in a region of the dielectric adjacent to the amplifier. Positive and negative ions move in opposite directions, and the region becomes polarized. Turning the second amplifier on and the first one off causes the polarized region to move down the transmitter, creating a "polarization current" that is a source of radio waves. The amplifiers can be triggered in such a way that this source moves the length of the transmitter faster than the speed of light.

Genie Pro

Satellite imagery data are being captured at higher quality and in greater amounts than ever before. Unfortunately, few organizations are capable of analyzing so much complex data.

A Los Alamos team has developed a remarkable image-analysis software system called Genie Pro that will make the job easier by reducing the time and skill required for analysis.

Genie Pro is a machine-learning software system that analyzes color and texture in image data to find features of interest. Genie Pro uses an evolutionary algorithm that evolves new software each time it's used.

An analyst uses a simple point-and-click graphical interface to identify a small set of example data in a satellite image, say a region of conifer forest or a particular agricultural crop. Genie Pro then learns a new software program that can detect and map out that feature using the selected satellite data. This new software program can then be applied to similar images, for example, to map a type of forest across a large region or entire country.

A NASA satellite image (left) was analyzed using Genie Pro (right). It identified land areas of interest: forests in blue, grasslands in green, scrub and bare ground in yellow/red.

Developed and funded by the Department of Energy and Department of Defense, Genie Pro has been used to analyze damage caused by natural disasters such as wildfires, hurricanes, and earthquakes; to evaluate terrorist attacks; and to monitor environmental changes and crop health. Genie Pro can also be applied to a wide range of non-satellite imagery, such as microscope images of tissue samples.

Future developments will expand its analytical capabilities to video and 3-D data and extend its application to more fields of science and industry. Los Alamos recently signed exclusive field-of-use license agreements for Genie Pro with the Virginia company Observera, Inc., which does remote sensing and image science, and with Aperio Technologies, Inc., a digital pathology company based in Vista, California.

An MRI for Your Luggage

If you've flown recently, you've encountered the "3-1-1 rule" for fluids (liquids, gels, and aerosols) in carry-on luggage. Containers of such things as toothpaste and cosmetics must not exceed 3 ounces each and must be packed together in a single quart-size plastic bag—one per traveler. The plastic bag is screened separately at the airport security checkpoint.

The rule dates from September 2006, after London authorities uncovered a plot to blow up airliners with liquid explosives.

The fluid containers packed in compliance with the 3-1-1 rule (top) are marked with colored dots in an MRI Screen scan to indicate level of potential threat.

A Los Alamos research team is hoping to make 3-1-1 unnecessary by developing a new kind of magnetic resonance imaging (MRI) machine—MRI Screen—adapted to the needs of airport security.

At hospitals, MRI scans provide images of internal organs. They do so by using radio waves and a strong magnetic field to coax hydrogen atoms into revealing their positions within the body. The Los Alamos machine uses the same principle to capture images of fluid products and will ultimately be applied to products packed deep inside a carry-on bag.

Because different chemicals produce different magnetic "signatures," MRI Screen even distinguishes between fluids—hand lotion versus liquid explosives, for example—by feeding data to a computer for determination of which fluids are safe and which are possible threats. It then marks the items in the image with a colored dot: red for unsafe, green for safe, and yellow for unknown. Security personnel can then remove the red-labeled items and double-check the yellow-marked ones.

The magnetic fields used in MRI Screen are at least 1,000 times weaker than the ones used for medical MRIs, resulting in a smaller, lighter, and less-expensive machine, perfect for security purposes. A prototype will be tested in August 2008 at an operational airport, possibly the Albuquerque Sunport.

Work on MRI Screen is sponsored by the Department of Homeland Security.