Key points
- Commonly known as Epsom salts, epsomite is highly soluble in water and can absorb water from the air.
- Epsomite is good for gardens as a magnesium supplement, and added to baths for a relaxing soak.
- Instruments on NASA's rovers have detected epsomite on Mars, indicating water was once on the planet's surface.
Named for the English town of Epsom, epsomite is found where lakes or volcanic activity have occurred. You might be more familiar with its common name of Epsom salts.
Epsomite forms fibrous, needle-like crystals that are usually white, but can be colourless. Sometimes, if it forms very slowly, it can present as large, very clear crystals.
It is a hydrated magnesium sulfate mineral, which is highly soluble in water. As well as being soluble in water, epsomite can absorb water from the air.
Gardening or bathing, epsomite does both
Epsomite is very useful in the garden. It is used as a magnesium supplement to improve plant quality, especially for tomatoes, peppers and roses.
After a long day of spreading epsomite around your garden, you might want to soak in a warm bath. Chances are you’ve added Epsom salts to your bath water at some stage.
It’s due to the solubility of Epsom salts that they are often mixed with fragrance and other cosmetics to make the sweet-smelling bath salts many of us love.
Understanding the Mars geology
Dr Jane Hodgkinson is a geologist and Principal Research Scientist and works with our In-Situ Resource Utilisation (ISRU) facility.
"I grew up in England, just a few kilometres from Epsom, so this mineral is a sentimental favourite for me," Jane says.
"Importantly, however, there is a strong connection between epsomite and the planetary science we are doing within the ISRU facility."
Epsomite is known to exist on Mars. Instruments on NASA’s Mars Opportunity and Curiosity rovers, and the Reconnaissance Orbiter, have detected magnesium sulfate minerals, including epsomite, on the planet's surface.
Forming in the presence of water, the occurrence of epsomite on Mars is a valuable indicator that water has existed on the surface of Mars.
"This is significant because if there was water, there may have been other conditions for life at some point in Mars’ history," Jane says.
Jane says that even if signs of early life are not found on Mars, the distribution and formation of epsomite deposits can tell us about past weathering processes. This contributes to our understanding of Mars’ geology and historical climate.
Potential to support life
"In the ISRU facility, we’re looking at technologies to support future space missions, such as systems that can sense and select minerals like epsomite," Jane says.
"Epsomite and other sulfates can contain up to 20 per cent water by mass, so it may provide a vital resource for human space missions."
These minerals, which contain hydrogen and oxygen (the make-up of water), could potentially be used for agricultural applications on-planet. They could help with water purification and as a supplement. Both are critical resources for human presence in space.
Back to a more terrestrial location, epsomite can be found at a place called Moon Plain, just outside Coober Pedy in South Australia. Moon Plain, known for its rocky moon-like landscape, provides plentiful epsomite and it’s found right on the surface.
Both NASA and the Mars Society Australia have contemplated performing in-situ trials on Moon Plain to simulate water-extraction with the epsomite found there.
Growing epsomite crystals at home
To get some pictures of epsomite crystals for our article, Jane grew some. It is easy, you just need patience and adult supervision. You’ll need some Epsom salts (magnesium sulfate) from a hardware store, supermarket or pharmacy.
Here's how Jane did it:
- In a bowl or beaker, mix about one quarter of a cup of Epsom salts with a quarter of a cup of hot tap water. You don't need boiling hot water.
- Stir to dissolve the salts. Some salt will remain solid, but that's okay.
- Place the container somewhere it won't get knocked or disturbed. Make sure no one mistakes the liquid as a drink of water (it's clear and odourless).
- Wait for the liquid to evaporate.
The speed of evaporation will depend on the room temperature and how dry the air is.
After a few hours, you might see some tiny crystals begin to form, but it will probably be a few days. If you are patient, you can potentially grow larger and very clear crystals.
Jane's crystals grew over two days, and were very, very small, and the pictures she took, were from a microscope. You might need to wait a few more days to see them with the naked eye.