"If it moves like water, it may very well be water." —Oregon State planetary science professor Joe Levy discusses the "recurring slope linneae" visible on the surface of Mars in recent high-resolution photographs. Some people think the lines, which run downhill into ravines, offer proof that water exists in frozen form on the red planet's crust, and melts into flowing liquid during warmer months. Of course, with James Cameron fresh back from his trip seven miles deep into the Mariana Trench, other possibilities come to mind.

"We could send senior-citizen volunteers to the Red Planet, where they could spend their final months conducting experiments, laying the groundwork for future permanent settlements and digging their own graves." That's from this great piece at Scientific American in response to the op-ed Lawrence Krauss (a Scientific American columnist) wrote in Monday's Times about sending astronauts on one-way trips to Mars. Apparently, the greatest obstacle to man's visiting the red planet lies not in launch capabilities or guidance systems or the threat of Martian attack, but rather in the dangers posed by exposure to the sun's powerful radiation on the return flight. Building a strong enough shield is [...]

Mars needs women: "Women will be among the first teams to take part in pioneering trips to Mars, experts have said. Any future missions to one of Mars' two moons are only likely to happen by 2033. And despite it being Neil Armstrong and his two male colleagues who first set foot on the Moon, some of the world's leading space experts believe that women could be on the first explorations to the 'red planet.'"

• Shifting, avalanching, freezing-and-unfreezing dark basalt sand dunes encircling the North Pole of the planet Mars

• Area flooded around the city of Rockhampton, in Queensland, Australia last month

• God's rusty steel ring

• The hole you left deep inside of my heart