DATA BANK

THE FIRST MARS EXPEDITION CONFIRMED MUCH OF WHAT earlier robot spacecraft had discovered about the red planet.

Mars is a cold world. It orbits roughly one and a half times farther from the Sun than the Earth does. Its atmosphere is far too thin to retain solar heat. On a clear mid-summer day along the Martian equator the afternoon ground temperature might climb to seventy degrees Fahrenheit; that same night, however, it will plunge to a hundred below zero or lower.

The atmosphere of Mars is too thin to breathe, even if it were pure oxygen, which it is not. More than ninety-five percent of the Martian air is carbon dioxide; nearly three percent nitrogen. There is a tiny amount of free oxygen and even less water vapor. The rest of the atmosphere consists of inert gases such as argon, neon and such, a whiff of carbon monoxide, and a trace of ozone.

The First Mars Expedition discovered, however, something that all the mechanical landers and orbiters had failed to find: life.

Tucked down at the floor of the mammoth Valles Marineris—the Grand Canyon that stretches some three thousand kilometers across the ruddy face of the planet—sparse colonies of lichenlike organisms eke out a perilous existence, hiding a few millimeters below the surface of the rocks. They soak up sunlight by day and absorb the water they need from the vanishingly tiny trace of water vapor in the air. At night they become dormant, waiting for the sun’s warmth to touch them once again. Their cells are bathed in an alcohol-rich liquid that keeps them from freezing even when the temperature falls to a hundred degrees below zero or more.

Fourth planet out from the Sun, Mars never gets closer to the Earth than fifty-six million kilometers, more than a hundred times farther than the Moon. Mars is a small world, roughly half the size of the Earth, with a surface gravity just a bit more than a third of Earth’s. A hundred kilograms on Earth weighs only thirty-eight kilos on Mars.

Mars is known as the red planet because its surface is mainly a bone-dry desert of sandy iron oxides: rusty iron dust.

Yet there is water on Mars. The planet has bright polar caps composed at least partially of frozen water—covered over most of the year by frozen carbon dioxide, dry ice. The First Mars Expedition confirmed that vast areas of the planet are underlain by permafrost: an ocean of frozen water lies beneath the red sands.

Mars is the most Earthlike of any world in the solar system. There are seasons on Mars—spring, summer, autumn and winter. Because its orbit is farther from the Sun, the Martian year is nearly twice as long as Earth’s (a few minutes short of 689 Earth days) and its seasons are consequently much longer than Earth’s. Mars rotates about its axis in almost the same time that Earth does. A day on Earth is 23 hours, 56 minutes, and 4.09 seconds long. A day on Mars is only slightly longer: 24 hours, 37 minutes, and 22.7 seconds.

To prevent confusion between Earth time and Martian, space explorers refer to the Martian day as a sol. In one Martian year there are 669 sols, plus an untidy fourteen hours, forty-six minutes and twelve seconds.

The discovery of the rock-dwelling Martian lichen raised new questions among the scientists: Are the lichen the only life form on the planet? Or is there an ecological web of various organisms? If so, why have none been found except the lichen?

Are these lowly organisms the highest achievement that life has attained on Mars?

Or are they the rugged survivors of what was once a much richer and more complex ecology?

If they are the sole survivors, what destroyed all the other life-forms on Mars?