Mars

Mars is a terraformed semi-terracompatible planet, in the Sol system. As of 2611, it has just under three million inhabitants, geneered for low gravity and low atmospheric pressure: Martians come from Lunar stock, though socially they are slowly drifting away from their founding culture. Lunar back up has unsured that Mars has a highly developed technoeconomy.

At first glance, Mars may look like a regular terracompatible planet, but 3/5ths of its surface is covered by deserts and the overall landscape is steppe, with scarce vegetation.

There are thousands of crater lakes and a narrow, meandering equatorial body of water, the Lowell Sea, formed by impact craters left by the terraforming process. As of 2611, Mars has six major urban areas and some towns and villages.

Moons
Phobos and Deimos are the asteroid-like moonlets of Mars. As of 2611 their combined population is half a million people, of Martian phenotype. Both were settled at the beginning of the terraforming project, being now heavily industralized and well defended.

Terraforming
In order to make it habitable for humans, Mars was terraformed at great expense by the Lunar Republic between 2091 and 2550. It stands as the most complex and expensive project ever undertaken by the human race.

The English Wikipedia article about tNA says that two lengthy subplots were dropped from the novel for space reasons. One of them would have involved Louise and Genevieve Kavanagh’s ship crash-landing on Mars. This was later confirmed and expanded by PFH in a private communication.