Jeans and Shirt on Mars_03Mike Nudelman/Business Insider

Mars is a cold world, full of deserts and containing very little oxygen or gravity.

The average annual temperature on Mars is -64°F. At its hottest, Mars could hit 80°F near the equator in the middle of the day. In the Martian winter, however, temperatures could fall to -199°F.

That's why the first requirement for visiting the Red Planet would be a space suit.

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 only do for a little more than a minute.

Here's what Chris Webster from NASA's Jet Propulsion Laboratory, which manages the Curiosity rover currently roaming Mars, had to say over email:

The most serious immediate impact would be from the low atmospheric pressure that is nearly a vacuum compared to Earth, and within minutes the skin and organs would rupture, outgas and produce a quick painful death.

If not killed by the low-pressure atmosphere, there are many other environmental factors that make Mars inhospitable to humans without protection.

Webster explains:

Any humans on Mars would have to contend with the lack of oxygen (only ~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 — and all this before they started looking for food and water!

That sounds pretty gruesome. We hope these women and men know what they're signing up for.