Buoyed by alcohol

The future of Mars exploration could lie in methanol-filled balloons, say
researchers at Pioneer Astronautics in Lakewood, Colorado. A team has
successfully tested a polyethylene balloon filled with methanol 30 kilometres
above the Earth. Warmed by the sun, the 700-litre balloon inflated in less than
a minute, says principal investigator Robert Zubrin. On Mars, with its mostly
carbon dioxide atmosphere, such balloons could carry heavy payloads because
methanol is lighter than CO₂.