Utah phenomenon at the Great Salt Lake returns in 2020, helps scientists study Mars

Utah (ABC4 News) — The state with the Great Salt Lake is known for its many natural wonders and phenomenons, so it’s no surprise the Utah Geological Survey has added another one of nature’s masterpieces to its long list of miraculous discoveries.

According to the Utah Geological Survey, mirabilite (hydrated sodium sulfate—Na₂SO₄•10H₂O), also known as Glauber’s salt, are rare salt mounds that can usually be found in polar regions or even on Mars.

Recently, they have been discovered at the Great Salt Lake.

Utah.com lists the Great Salt Lake as the largest saltwater lake in the Western Hemisphere, and the eighth-largest terminal lake in the world. It is around 75 miles long, 35 miles wide, and remains salty because it has no outlet.

Scientists say mirabilite is a vitreous, colorless to white monoclinic mineral that forms as an evaporite from sodium sulfate-bearing brines.

The rare mounds were first discovered at the Great Salt Lake in late October 2019. Utahns and scientists who first noticed the mounds appearing near the beaches of the Great Salt Lake were left wondering what they were.

The Utah Geological Survey began to study the unique formations through the winter of 2019-2020 before they disappeared.

The mounds have returned again in 2020.

Officials with the Utah Geological Survey say that as air temperatures started to cool and near freezing temperatures, unique mineral mounds began forming on the south shore of Great Salt Lake, just east of the Great Salt Lake Marina.

The discovered mineral mounds are composed of mirabilite hydrated sodium sulfate—Na₂SO₄•10H₂O, found in the Great Salt Lake, which is different from table salt or sodium chloride—NaCl.

According to the Utah Geological Survey, “when the sodium-sulfate-rich spring water hits the cold winter air, mirabilite crystals form and build up a collection of small terraces, similar in appearance to the travertine rimstone and dam terraces that form at Mammoth Hot Springs in Yellowstone National Park.”

In the 1940s, researchers investigated this area of the Great Salt Lake. Reports show they found a 3 to 6-foot thick mirabilite layer 30 inches down in the subsurface, the survey shares.

In this area, groundwater appeared to be partially dissolving the mirabilite layer. As the mirabilite layer reprecipitated at the surface, the spring water emerges.

“Mirabilite is most stable and precipitates in sub-freezing dry environments. When temperatures rise above freezing, the impressive clear mirabilite crystals that form the mounds will dehydrate to form a white, powdery, easily eroded mineral called thenardite (Na₂SO₄). Furthermore, the mounds will only form if the area (at about 4194 ft) is above lake level,” the Utah Geological Survey adds.

Officials say the forming of the mounds was a very rare occurrence in Utah, until the past few years.

“In saline lakes, mirabilite crystals form in the water column, float to the surface, and are washed ashore to form an amorphous, slushy slurry or dune-like accumulations of crystals,” the survey states.

According to the survey, mirabilite can be quite common and can be found in saline lakes all around the world, and possibly, even outside of this world. Saline lakes or salt lakes consist of landlocked bodies of water that have a concentration of salts and other dissolved minerals much higher than most lakes.

Officials say it isn’t uncommon for saline lakes to have a higher concentration of salt than seawater.

Researchers say conditions on Mars are conducive to the formation of mirabilite, even though the unique mineral hasn’t been documented there. Mars does have topographic mounds that some researchers believe may be related to saline groundwaters.

Due to the similarities, some researchers are interested in the growth of mirabilite mounds on Earth because they feel it might help them understand the geologic processes on Mars.

Officials with the Utah Geological Survey and the Utah Department of Natural Resources say they want to remind everyone who might be interested in seeing the mirabilite in-person to remember the mounds are extremely fragile and that researchers are still studying them.

They ask those wanting to visit the Great Salt Lake to please not walk on the mounds or take samples home with them. Mirabilite is unstable as temperatures rise above freezing and dehydrate to form a white powder, so even those who attempt to take a sample home would find the mineral doesn’t last longer than a day.