Geoffrey A. Landis recently returned to Ohio from a trip to Boston, where he was filmed showing Michio Kaku how a balloon filled with ordinary air floats in a carbon-dioxide atmosphere for Kaku’s television special Sci-Fi Science: Physics of the Impossible. In the rest of his life, Geoff works on NASA missions to Mars, Venus, and the solar corona. On rare occasions, he finds time to write science fiction stories that, as in the following novella, sometimes take place in these exotic locales.

When Leah Hamakawa and I arrived at Riemann orbital, there was a surprise waiting for Leah: a message. Not an electronic message on a link-pad, but an actual physical envelope, with Doctor Leah Hamakawa lettered on the outside in flowing handwriting.

Leah slid the note from the envelope. The message was etched on a stiff sheet of some hard crystal that gleamed a brilliant translucent crimson. She looked at it, flexed it, ran a fingernail over it, and then held it to the light, turning it slightly. The edges caught the light and scattered it across the room in droplets of fire. “Diamond,” she said. “Chromium impurities give it the red color; probably nitrogen for the blue. Charming.” She handed it to me. “Careful of the edges, Tinkerman; I don’t doubt it might cut.

”I ran a finger carefully over one edge, but found that Leah’s warning was unnecessary; some sort of passivation treatment had been done to blunt the edge to keep it from cutting. The letters were limned in blue, so sharply chiseled on the sheet that they seemed to rise from the card. The title read, “Invitation from Carlos Fernando Delacroix Ortega de la Jolla y Nordwald-Gruenbaum.” In smaller letters, it continued, “We find your researches on the ecology of Mars to be of some interest. We would like to invite you to visit our residences at Hypatia at your convenience and talk.”