Combatting Anthrax

Anthrax spores, pictured here in a thin section micrograph, are inactive forms of the bacterium Bacillus anthracis. Such bacteria can survive for decades inside a spore's tough protective coating; they become active when inhaled by humans.

Hayman explains: "[Space faring] astronauts will eventually need to grow some of their own food in greenhouses. But there's a problem: the leaves of growing plants release ethylene (C2H4) - a gas that causes fruits and vegetables to mature." In the close quarters of a spacecraft (or inside an enclosed plant growth chamber), ethylene would build up and ripen greenhouse plants prematurely.

Space greenhouses needed a new technology to remove that ethylene.

In the 1990's, University of Wisconsin professor Marc Anderson and colleagues from the Wisconsin Centre for Space Automation and Robotics (WCSAR) made a crucial discovery: They found that ultra-thin layers of titanium dioxide (TiO2) exposed to ultraviolet light would efficiently convert ethylene into carbon dioxide (CO2) and water (H2O) - substances that are good for plants. Titanium dioxide itself is a harmless, non-toxic colouring agent used in many consumer products. It is a catalyst for the ethylene-destroying reaction; no TiO2 is consumed.

TiO2-based ethylene removers have since flown to space inside a pair of plant growth chambers: ASTROCULTURE™ on board NASA's space shuttle and ADVANCED ASTROCULTURE™ on the International Space Station (ISS). The devices were built by WCSAR - a NASA Commercial Space Centre at the University of Wisconsin. WCSAR is one of 17 such centres around the country sponsored by NASA's Space Product Development program to encourage the commercialisation of space by industry.