Dirt Money was the currency of the civilization of Mars, before the disaster struck. Like all aspects of their civilization, their currency is based on the plant cycle and therefore is made from that of the more long-lived groves, rendering it much more valuable.
In Martian Dreams, the Avatar had to find some dirt money for the Xorinite Wisp in the Abandoned City in order to learn more about Mars and its civilization.
|| Soil, as Doctor Spector explained, was very important to the Martians' development. A seed planted in the composted soil, fertilized and watered, and ritually visited once every three days, would, nine days later, sprout and form a large, rounded pod. When this pod was split open, a young Martian, with background and knowledge comparable to that of a young adult in our culture, would climb forth. Because of this, soil became the basis for the Martian economy, with the soil from older, more established groves being worth the most. (Hence, the dirt money that we came across from time to time.)|
- Dirt money can be found in the mines where the Avatar frees the two explorers from the cave-in in order to get access to Olympus.