Life at the Limits: Earth, Mars, and Beyond

an educator workshop and fieldtrip

Four Mile Flat
Carson Sink
An Extreme Saline and Alkaline Environment

Reported by: Amber Sierra, Donna Roberts, Betsy Sullivan


We visited Huck Salt Company in the Four Mile Flat off US50. The Four Mile Flat is in the Carson Sink near Fallon, Nevada and is lower than the surrounding ranges.

The surrounding mountains and hills drain water into the flat area, trapping the water as it has no outlet. As the water runs off the mountains, it collects salts and minerals, as well as soil particles. Water also is added by subsurface springs that emminate from small faults. As the water pools and evaporates, the salts and minerals settle out of solution. This brine leaves behind a thick layer of NaCl, which, in some areas, reaches a thickness of 70 feet (other salt minerals may be present as well).

The salt can be harvested and sold. The Huck Salt Company harvests salt from 965 acres of salt flat. The area is mostly a flat plain of white salt with puddles and streams of red or pink water. Salt crystals taken from various depths range from white at the top, then pink, and sometimes green at the lower level. Color changes in the water and salt indicate the possible presence of microbial life. Our testing showed the pH of the red stream was alkaline at 9.2.

Four Mile Flat of Carson Sink, on the property of the Huck Salt Company.
Sampling “red water” at Huck Salt Company.
Four Mile Flat of Carson Sink, on the property of
the Huck Salt Company.
Sampling “red water” at Huck Salt Company.
View of “red water” at Huck Salt Company.
View of “red water” at Huck Salt Company.
View of Four Mile Flat from Huck Salt Company.
Harvested salt for human use.
Salt from the ground
Harvested salt for human use.
Salt from the ground



The organisms identified as living in this area are archaea (ex. halobacterium), cyanobacteria (ex. halothece), and eukaryotic alga (ex. Dunalliela salina ). All organisms need freshwater to survive. These salt-tolerant organisms — halophiles — have developed a method of maintaining the chemical balance in their cells. They can sustain homeostasis (their internal equilibrium) in spite of living in an environment where fresh water is inaccessible. They may have developed extra carbohydrates to maintain hydration, or cell walls to help exclude the salts, or they may have a “sodium pump to help eject the salt, leaving the freshwater behind in the cell.

The water is alkaline. Calcium carbonate carried into the basin dissociates during evaporation. The calcium precipitates as particles that settle to the bottom of the water, leaving behind carbonate ions in solution in the water. This produces an alkaline solution.


The loss of water from a system body (planet or moon) may leave a saline layer on the body's surface. The environment found at Four Mile Flat (Huck Salt Company) represents a high saline environment that may exist on other system bodies. The research into halophiles existing in the saline environment will guide the development of tests to identify life forms in unexplored environments.


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