Thomas R. O'Donnell

Roundup: Mars meteors, robotic gardeners, a tight squeeze for molecules, and atom bomb history

In University research on November 13, 2014 at 6:13 am
MARSIS spectrographs showing ionosphere fluctuation due to contact with cometary debris.

Spectrographic MARSIS data from radar soundings of the Martian ionosphere midway between the equator and north pole at three different times. The horizontal axis is the MARSIS radio wave pulse frequency. The vertical axis is the estimated altitude above the planet’s surface. Increasing intensity is indicated by color-coding from blue to red, as shown by the scale. The normal ionospheric reflection can be seen extending up to about 2.8 megahertz on all three spectrograms, corresponding to an electron density of about 100,000 electrons per cubic centimeter. The top spectrogram shows conditions about eight minutes before the comet’s closest approach. The middle spectrogram shows conditions about seven hours later, when a temporary layer of enhanced electron density had formed within the ionosphere. It extends to very high frequencies, from about 2.8 to 3.8 megahertz, and corresponds to an electron density of about 200,000 electrons per cubic centimeter. This layer is at an altitude below the normal peak in the ionosphere. By comparison with the ground reflection, which can be seen at frequencies above 4 megahertz, the layer of enhanced ionization is estimated to be at an altitude of 50 to 60 miles. Credit: ASI/NASA/ESA/JPL/Univ. of Rome/Univ. of Iowa

Here’s a little bit of everything (almost) going on in Iowa science, from the interplanetary to the tiny and from the latest in robotics to the history of Iowa’s role in the atom bomb.

University of Iowa researchers last week released results from a probe that tracked the impact of a comet flyby on Mars’ atmosphere. The impact was something like a massive meteor shower.

On Earth, Iowa State University plant scientists plan to staff a high-tech growing facility with a robot. (Don’t worry, postdocs and grad students; I’m sure they’ll need some human help, too.)

Ames Laboratory researchers, meanwhile, have taken a mathematical look at the uncomfortable situation that occurs when tiny particles meet in a nanoparticle’s narrow pores. It’s a bit like people trying to squeeze past each other in a tight hallway.

And finally, for hardcore historians, there’s a look back at the war-era events behind the lab’s founding.First, it’s off to Mars. U of I physicists last week reported findings from their MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding Instrument) probe. It’s part of the Mars Express spacecraft, launched by the European Space Agency and in orbit around the red planet since 2003.

Mars Express and MARSIS were in position for an exceedingly rare event: The close (in astronomical terms) flyby of a comet, specifically C/2013 A1, called Siding Spring. On October 19 the dirty iceball passed just 84,500 miles above Mars and shed dust and debris onto the planet.

MARSIS tracked the planet’s ionosphere – an atmospheric layer of free electrons and charged atoms – using high-tech radar. (Earth also has an ionosphere that reflects radio waves.) As this U of I release and Iowa City Press-Citizen story detail, MARSIS found a huge jump in density of electrons in Mars’ atmosphere just hours after Siding Spring’s close pass.

The team concluded the ions came from the massive comet dust cloud. When the high-speed particles hit molecules blanketing the planet, they burned up, stripping electrons from their atoms and creating an abundance of free electrons and charged atoms.

In essence, the burning comet debris created a new, short-lived ionosphere around Mars, MARSIS found.

If you want the details on what the various Mars Express probes found (including concentrations of elements detected in the comet detritus, ionosphere radar images, and Curiosity’s pictures of the passing comet), check out this page from NASA.

As the Press-Citizen article notes, anyone on the planet surface would have seen a heck of a meteor shower light show – but there are no Martians to see it, of course. NASA’s Curiosity robotic rover could have enjoyed it, if it weren’t so sarcastic about being abandoned on a lonely planet.

Speaking of robots (nice transition, right?), ISU researchers are designing automatons to track plant growth in a specialized facility they’re calling the Enviratron.

A schematic of the Envriatron plant research facility.

The Enviratron: A robotic rover will travel through growth chambers, gathering huge amounts of plant development data via sensors. Credit: Stephen Howell, Iowa State University.

Like the zombie tractor I wrote about earlier this year, the idea is to capture characteristics of plants growing under varying conditions. The robot will travel through a set of plant-filled growth chambers, each controlling environmental factors like temperature, moisture, carbon dioxide concentration and light. Sensors on the steely horticulturalist will gather data on the plants’ progress.

Lie Tang, an ISU professor of agricultural and biosystems engineering, is building the Enviratron robot, just as he did the zombie tractor. Plant scientists working on the project include Steve Whitham, a plant pathology and microbiology professor, and Stephen Howell, a genetics, development and cell biology professor. (Howell is the former director of ISU’s Plant Sciences Institute; I worked with him in my freelance days.)

Other principal investigators are bioinformatics specialist Carolyn Lawrence in genetics, development and cell biology, and Thomas Lubberstedt in Agronomy.

The usual Iowa crops – corn, soybeans and biomass – are likely candidates for Enviratron treatment. The National Science Foundation is footing the construction bill with a grant of nearly $1 million. A prototype should be up next year and the entire facility, with up to eight growth chambers, in three years.

Frankly, I’d be a little nervous that Enviratron might turn into Megatron. That couldn’t happen … right? But it would be WAY COOL.

Meanwhile, Ames Laboratory is reporting a small (literally) accomplishment in modeling molecules. The research could have implications for the many industrial processes that use catalysts – substances that boost the rate of a chemical reaction but aren’t consumed in the process.

The focus, as the lab lays out in a well-written release, is on mesoporous nanoparticles. Nanoparticles, as you may know, are clumps of atoms thousands of times smaller than the diameter of a hair. Some of these nanoparticles are engineered to have even tinier pores in them, like sponges (except they’re not necessarily soft and squishy).

The pores are lined with a catalyst, providing multiple sites for chemical reactions. The more pores, the more the catalyst comes into contact with the reactants, supercharging the reaction.

But scientists have to find a balance between the number of pores and their size. Too small, and molecules will have a hard time squeezing past each other to move in and out of the pores. Too few, and the catalysts aren’t as effective.

Ames Lab scientist Jim Evans and colleagues used computer models to study the pores and how molecules move through them. By running the model millions of times, the scientists determined the probability of molecules passing for different-sized pores.

That wasn’t good enough, given the problem’s complexity. So Ames Lab theoretical chemistry and applied mathematics experts applied other tools to understand how narrow the pores must be to keep the particles from passing – and stalling the catalytic reaction.

The researchers published their results in the journal Physical Review Letters.

The Ames Lab has come to specialize in this kind of work: materials science, whether experimental or theoretical. It goes back to its roots as one of the key facilities in providing the raw materials for the first atom bombs.

The history of that birth is now available on line, thanks to the Department of Energy.

In 1944, Manhattan Project leader Gen. Leslie Groves commissioned a history. Most of that document is now declassified and DOE’s Office of History and Heritage Resources has digitized its one copy.

The PDFs are difficult to read; they appear to be bad carbons or mimeographs. But those who want to understand Iowa State College’s role in the secret bomb venture can delve into Volume 4, Chapter 11: Ames Project (PDF).

I haven’t looked at this closely yet, but much of the material appears to be technical – perhaps beyond the interest of the average reader. Yet, the introduction makes clear that the college devised many of the chemical and metallurgical processes for producing bomb materials – including purified uranium for enrichment.

By the end of 1945, at Iowa State “over two million pounds of uranium metal billets were produced, thorium metal and services were supplied, and the entire research program was supported” by contracts totaling about $4 million, the history says. Considering that at the time uranium produced under standard industrial processes cost $22 a pound, “it is obvious that the Ames contracts were decidedly profitable even from a direct financial viewpoint.”

This history may be familiar to some, but it’s a great chance to look back from a perspective very near to the actual events.



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