• Like the Earth, the planet Mars has an atmosphere, white clouds, polar caps and seasons.

• Mars has a partially liquid core, probably containing molten iron and perhaps surrounding a solid iron core, as within the Earth.

• Mars does not now have a global dipolar magnetic field to deflect lethal cosmic rays and energetic solar particles.

• The oldest terrain on Mars exhibits bands of magnetized material with alternating polarity, most likely originating about 4 billion years ago when the red planet might have had a global dipolar magnetic field.

• In the early 20th century it was thought that seasonal water melting from the polar caps in spring and summer produced a dark band of vegetation on Mars, and that intelligent Martian inhabitants had constructed canals to transport water across the planet.

• The seasonal dark regions on Mars are now attributed to winds, and the canals are now known to be an illusion caused when the eye arranges small, disconnected features into lines.

• Mars now has a thin, cold and dry atmosphere that is composed almost entirely of carbon dioxide, with a surface pressure of about a one-hundred-fiftieth of the Earth's atmosphere and a mean surface temperature that is well below the freezing temperature of water.

• Because of the low surface pressure and temperature of the Martian atmosphere, it cannot now rain on Mars. If any liquid water were now released on the planet's surface, it would survive for just a brief time before freezing or evaporating. […]