How long could a human survive on Mars wearing only jeans and a T-shirt?

Though water is one ingredient needed for life, the red planet is still a rough place for humans: it's cold, full of deserts, and has very little oxygen or gravity.

The average annual temperature on Mars is -64 degrees Fahrenheit (-53 degrees Celsius).

At its hottest, Mars could hit 80 degrees Fahrenheit (26.6 degrees Celsius) near the equator in the middle of the day.

In the Martian winter, however, temperatures could fall to -199 degrees Fahrenheit (-128.3 degrees Celsius).

Obviously the first requirement for visiting Mars would be a spacesuit. There are teams of scientists dedicated to designing just the right getup for deep space missions.

But we were curious: How long could someone survive a summer day on Mars without all this fancy equipment, say, wearing only jeans and T-shirt and while holding his or her breath, which the average human can do for a little more than a minute.

Well, not very long.

"The most serious immediate impact would be from the low atmospheric pressure that is nearly a vacuum compared to Earth," Chris Webster from NASA's Jet Propulsion Laboratory, which manages the Curiosity rover roaming Mars, said in an email.

And what would happen to your insides?

"Within minutes the skin and organs would rupture, outgas, and produce a quick, painful death," says Webster.

If not killed by the low-pressure atmosphere, there are many other environmental factors that make Mars a really terrible place for humans, at least without protection.

"Any humans on Mars would have to contend with the lack of oxygen - only about 0.1% compared to Earth's 20% - the very cold surface temperatures, the ubiquitous and irritating dust, the intense UV radiation, surface chemicals and oxidants," Webster said. "And all this before they started looking for food and water!"