Crystals and the search for life

Professor Aaron Celestian


Adjunct Asosciate Professor (Teaching) of Earth Sciences

Contact Information


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Professor Celestian researches how minerals interact with their environments and with living things, and how those minerals can be used to solve problems like climate change, pollution, and disease.

Background to Science and technology and facilities council

The Science and Technology Facilities Council (STFC) is a United Kingdom government agency that carries out research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy (both ground-based and space-based).


The Rutherford Appleton Laboratory (RAL) is one of the national scientific research laboratories in the UK operated by the Science and Technology Facilities Council (STFC). It began as the Rutherford High Energy Laboratory, merged with the Atlas Computer Laboratory in 1975 to create the Rutherford Lab; then in 1979 with the Appleton Laboratory to form the current laboratory.

It is located on the Harwell Science and Innovation Campus at Chilton near Didcot in Oxfordshire, United Kingdom. It has a staff of approximately 1,200 people who support the work of over 10,000 scientists and engineers, chiefly from the university research community. The laboratory’s programme is designed to deliver trained manpower and economic growth for the UK as the result of achievements in science.

It has a large range of experiments that look at all sorts of things from the very small building blocks of matter to the vast scales of astronomy.

Rutherford Appleton is not the only lab. There six sites in total and apart from RAL there is another large laboratory at Daresbury in Cheshire, the Royal Observatory in Edinburgh and the Boulby underground laboratory which is 1.1 kilometres underground in a working salt mine in Yorkshire.

There is a small team that works on the radio telescopes in Chilbolton in Hampshire and there is Polaris house in Swindon, which is not a lab, but it’s where all of the funding comes from.

Some of the sites mentioned above host their own series of online talks and events.



This talk was about crystals and the search for life.

How life was discovered in many new and wonderful environments where we didn’t think life could possibly exist before.

One unusual environmental is inside minerals and the bacteria trapped in these crystals could tell us a lot about where life could live elsewhere in our solar system.

The audience was asked whether they thought another planet or moon would most likely provide conclusive evidence of life outside of the Earth? Whether this evidence would be biological chemicals in rocks or the soil? Whether there would be geochemical signatures? Whether there would be changes in the atmospheric chemistry. Or if the evidence would be in the form of fossils of organisms? Or something else? Answers weren’t shared in the recording

The following are notes from the on-line lecture. Even though I could stop the video and go back over things there are likely to be mistakes because I haven’t heard things correctly or not understood them. I hope Professor Celestian and my readers will forgive any mistakes and let me know what I got wrong.

In the questions mentioned above the audience weren’t asked about whether there were actual life forms outside of the Earth because that would be pretty conclusive evidence that they existed. If something is seen swimming about in water then that is evidence that they are alive.

However, there are some environments, even on Earth that we don’t have the ability to observe and measure, to obtain evidence for life.

It might be that the environments that supported life no longer exist so how do researchers go about finding life that had existed in the past.

A lot of this work occurs through collaborations.

Professor Celestian works at the Natural History Museum of Los Angeles County in the United States in California but he also has an appointment at the Jet Propulsion Laboratory, which is a NASA facility. He is also associate professor of Earth Sciences at the University of Southern California.


The Natural History Museum of Los Angeles County is the largest natural and historical museum in the western United States. Its collections include nearly 35 million specimens and artifacts and cover 4.5 billion years of history. This large collection is comprised not only of specimens for exhibition, but also of vast research collections housed on and offsite.

The museum is actually associated with two other museums in Greater Los Angeles: the Page Museum at the La Brea Tar Pits in Hancock Park and the William S. Hart Ranch and Museum in Newhall. The three museums work together to achieve their common mission: “to inspire wonder, discovery, and responsibility for our natural and cultural worlds.

The Jet Propulsion Laboratory (JPL) is a federally funded research and development centre and NASA field centre in the city of La Cañada Flintridge, with a Pasadena mailing address, in California, United States.


The University of Southern California (USC, SC, or Southern Cal) is a private research university in Los Angeles, California. Founded in 1880 by Robert M. Widney, it is the oldest private research university in California.

Through his various appointments Professor Celestian has been able to collaborate with a range of people in order to solve problems related to looking for life.

He is a mineralogist. His work involves studying minerals and how they grow in different environments. His expertise assists biologists in looking for life that could exist in or around minerals.


The above image shows salt crystals which were collected in Southern California.

Salt is quite common, and is found all over the solar system

The white cubic shapes are white salt crystals. The pink material that is underneath the cubic salt crystals is bacteria filled salt. The bacteria produced a chemical called beta carotene and that’s the same kind of chemical that makes carrots orange and makes Robin’s feathers red.

Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically, a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth’s crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.


β-Carotene is an organic, strongly coloured red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 carbons. Among the carotenes, β-carotene is distinguished by having beta-rings at both ends of the molecule. β-Carotene is biosynthesized from geranylgeranyl pyrophosphate.

It is a is a very distinct biochemical marker and it is preserved in rocks. So, researchers look for it in different lakes and other different environments.


The image above shows a modern salt lake. The water in the top part of it is really orange and pink in colour. And that is because of the bacteria that live there.

The bacteria are producing huge amounts of beta carotene in order to survive. How does beta carotene help them survive? Well, one reason is that the beta carotene is actually filtering ultraviolet rays. This would come in useful for any living organism that is living in a region where the surroundings are drying out or have dried out as in a hot, sunny, desert like the Sahara or a barren planet like Mars which has no atmosphere.

Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from our Sun.

The Sahara is a desert on the African continent. With an area of 9,200,000 square kilometres, it is the largest hot desert in the world and the third largest desert overall, smaller only than the deserts of Antarctica and the Arctic.


A satellite image of the Sahara by NASA WorldWind

The above link is a video over the Sahara and the Middle East was taken by the crew of Expedition 29 on board the International Space Station.


Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury.

Mars, having no atmosphere, is going to receive a lot of ultraviolet radiation. We, on Earth have some protection because of the ozone layer.

The ozone layer or ozone shield is a region of Earth’s stratosphere that absorbs most of the Sun’s ultraviolet radiation.


Some ultraviolet light does get through and a lot of it can be received by some bodies of water. Anything living in that water needs to have some form of protection to live. On Earth those bacteria protect themselves by producing beta carotene.


The bottom left of the above image shows a salt lake. These can be huge. The Great Salt Lake in the United States is one of the largest salt lakes in the world.


Satellite photo from August 2018 after years of drought, reaching near-record lows. Note the difference in colours between the northern and southern portions of the lake, the result of a railroad causeway.

Salt lakes can be as small as puddles or the size of a backpack


The above image shows the result of an experiment that Professor Celestian did with his son a few years ago. They wanted to see what would happen when the water evaporated from the salt water. Would anything happen to the bacteria or the beta carotene?

The right-hand side was the control from a salt lake with no bacteria in it and on the left-hand side was the liquid taken from Searles lake which is in Southern California.

Searles Lake is an endorheic dry lake in the Searles Valley of the Mojave Desert, in northwestern San Bernardino County, California. The lake in the past as also be called Slate Range Lake and Borax Lake.

image image

They just went to the lake to collect some of the pink water. They put it in a Petri dish and let the water evaporate off.


Initially there was just a pretty pink colour but as the water evaporated some pink cubic crystals started to appear on the right side of the petri dish (a little mark from the Professor’s mouse is indicating a crystal). There is no pink colour in the regions where the water has evaporated. This is a good indication that as the crystals were growing the beta carotene and the bacteria were presumably going into the crystal structures. They were following some of the water into the crystal structures because salt crystallises as the dihydrate NaCl·2H2O.

Sodium chloride commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions.


Crystal structure with sodium in purple and chloride in green

The bacteria and beta carotene don’t coat the whole dish pink.

When researchers are looking at evaporating lakes (which are not necessarily water lakes) on other planets and moons they are looking for similar behaviour, where the colour moves into the crystals only. The crystals will be where the bacteria will be concentrated.

The above link is a short animation that the professor made with an artist to explain the process outlined above.


The animation takes the audience through a salt lake, which is evaporating. Bacteria are producing the beta carotene.


As the water evaporates crystals are forming. The bacteria follow some of the water into the crystals.


Little bits of water stick to the crystals. So, you can think of a crystal as forming layers in a stair-step pattern. There is some water that fills into the little cracks and crannies in the crystal. Water and bacteria are trapped.



The crystal just continues to grow in all directions and incorporates layers of the bacteria laden liquid.



There are little pockets of fluid within each crystal. And if you look deep inside the crystal then you can see little pockets of fluid flying pass as you move deeper and deeper into the crystal.



Within the little “squares” of fluid are the miniscule bacteria, smaller than dust particles.


Shining ultraviolet light onto the trapped bacteria causes them to produce the beta carotene for a short time staining the crystal pink.


A laser (perhaps attached to a planetary rover) analyse the crystals without breaking them open.



On Mars the researchers are looking for bio-signatures and bio-markers of some kind of bacteria that could be producing chemicals inside crystals.

If some is found, samples can be collected. If not, the rover can move on and analyse another region of the surface. This is what is actually going to happen with the Mars 2020 mission.

Mars 2020 is a Mars rover mission by NASA’s Mars Exploration Program that includes the Perseverance rover and the Ingenuity helicopter drone. It was launched on 30 July 2020 at 11:50 UTC, and will touch down in Jezero crater on Mars on 18 February 2021.


Portrait of Perseverance and Ingenuity (Artist’s Concept) In February 2021, NASA’s Mars 2020 Perseverance rover and NASA’s Ingenuity Mars Helicopter (shown in an artist’s concept) will be the agency’s two newest explorers on Mars. Both were named by students as part of an essay contest. Perseverance is the most sophisticated rover NASA has ever sent to Mars. Ingenuity, a technology experiment, will be the first aircraft to attempt controlled flight on another planet. Perseverance will arrive at Mars’ Jezero Crater with Ingenuity attached to its belly. NASA’s Jet Propulsion Laboratory built and will manage operations of Perseverance and Ingenuity for the agency. Caltech in Pasadena, California, manages JPL for NASA. For more information about the Mars 2020 Perseverance mission, go to For more information about Ingenuity, go to

The mission is going to Mars, specifically with a laser spectrometer to investigate the crystals and see if there are any bio-signatures and chemicals.

Perseverance will investigate an astrobiologically relevant ancient environment on Mars and investigate its surface geological processes and history, including the assessment of its past habitability, the possibility of past life on Mars, and the potential for preservation of biosignatures within accessible geological materials.

The mission has to decide what crystals to look for and make sure that the rover is able to distinguish those from non-biochemical ones.

This is why Professor Celestian studies the crystals on Earth in great detail in weird environments. To see how they form.


So, this is the crystal again with its bacteria producing pink beta carotene. It is a classic example. Just a regular old halite. The table salt that you put on your food.

Halite commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride (Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on inclusion of other materials, impurities, and structural or isotopic abnormalities in the crystals. It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, and borates. The name halite is derived from the Ancient Greek word for salt.

The image below left shows another form of halite from a mine in Poland. It’s green, not because of bacteria, but because of another mineral called tolbachite, a copper chloride mineral that’s gets incorporated into the crystal staining it green

Copper (II) chloride is the chemical compound with the chemical formula CuCl2. This is a light brown solid, which slowly absorbs moisture to form a blue-green dihydrate.

Both the anhydrous and the dihydrate forms occur naturally as the very rare minerals tolbachite and eriochalcite, respectively


The image above right is another halite collected from Arizona in the United States.


Arizona is a state in the southwestern region of the United States.

The Arizona crystal is clear except for some blue/purple regions caused by radiation damage. There are natural radioactive elements in the environment and these sometimes get concentrated in the crystals.

Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.

Background radiation originates from a variety of sources, both natural and artificial. These include both cosmic radiation and environmental radioactivity from naturally occurring radioactive materials (such as radon and radium), as well as man-made medical X-rays, fallout from nuclear weapons testing and nuclear accidents.

The radiation inside the crystal, from radioactive elements, distorts the crystal structure, causing the blue colour. So not only do you have to know what crystals to look into. But you also have to know what the source of the colour is. You don’t want to find false positives. Also, in the Arizona crystal, in the gap between the purple areas there are little squared inclusions. These are little pockets of fluid that had been trapped inside of the crystal at the time it was formed.


This area would be investigated to see if there are any bacteria inside the crystal.

There are other salt crystals that are not stable on the Earth’s surface. Unstable salts or just anything that forms from evaporating liquid need careful conditions to appear.

The following image is of a rare crystal called Mirabilite

Mirabilite, also known as Glauber’s salt, is a hydrous sodium sulfate mineral with the chemical formula Na2SO4·10H2O. It is a vitreous, colourless to white monoclinic mineral that forms as an evaporite from sodium sulfate-bearing brines. It is found around saline springs and along saline playa lakes. Associated minerals include gypsum, halite, thenardite, trona, glauberite, and epsomite.

Mirabilite is unstable and quickly dehydrates in dry air, the prismatic crystals turning into a white powder, thenardite (Na2SO4). In turn, thenardite can also absorb water and converts to mirabilite.



Crystal structure of mirabilite

Mirabilite is not stable at the surface of the earth (but it may be stable in other places in the Solar System). Professor Celestian grew the crystal in his lab.

As soon as the Mirabilite solution starts to evaporate the crystal starts to form and grow. As soon as you take it out it converts to thenardite.


The above two images show the transition between the nice clear mirabilite crystal to the opaque thenardite crystal. The transition happens within minutes when all the water has evaporated away.

However, mirabilite might be stable in really cold conditions like those found on the moons that orbit Saturn and Jupiter and maybe even during the winter months on Mars.


The above image shows a gypsum crystal, which was found in the United States. It’s also called hourglass gypsum, because it’s got these inclusions of sand in the shape of an hourglass.

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.

The sand and clays stuck inside a crystal can hold large amounts of DNA. But the researchers don’t normally look for DNA. Most of the time they’re thinking about and dealing with objects that have been around for a million years or so. This means that any materials stuck inside of a crystal have been trapped there for a million years or so too. It is unlikely to be DNA because this breaks down quite readily. There are other biochemical markers that the researchers are interested in.


The above image shows epsomite

Epsomite is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O.

Epsomite is the same as the household chemical, Epsom salts, and is readily soluble in water. It absorbs water from the air and converts to hexahydrate with the loss of one water molecule and a switch to monoclinic structure.


Crystal structure of epsomite

You can buy Epsom salts at the pharmacists and supposedly helps you relax if you put it in your bath water.

Epsom salts are pretty common other planets as well and turns out bacteria really like it.

What can live in a crystal?


The above images show what some bacteria look like.


The above image shows a salt crystal produced from a salt lake that the professor grew in his lab. It’s a halite crystal, just sodium chloride.

It looks nice and cubic or cuboid.

Taking a closer look, as in the image below, there are lines that are stuck in the crystal on the right-hand side that kind of go from bottom left to top right. These are trapped fluids



Taking an even a closer look at those trapped fluids.


You can see that inside the fluid indicated by the professor’s mouse (it is moving around the jagged area at the top of the crystal) there is an accumulation of a pinkish colour.

Now, if you were to zoom in even further, what you would see is this. The image below shows one of the fluid inclusions inside the crystal and inside this there are little dancing dots. These are the bacteria that are still trapped inside the crystal moving around. There are about 4 of them. They are only about one micron in size. They are absolutely tiny.



The above image is another fluid. It’s not easy to see but there are lots of little dots just dancing all over the place, little bacteria trapped inside of these crystals


Professor Celestian took this last crystal from the middle sciences collection at the museum he is associated with. The crystal was at least 150 years old because it had been mined out of the earth 150 years ago and the bacteria are still quite happy living there.

Researchers have collected crystals that are hundreds of thousands of years old and living bacteria are still in them.


The above image is an artist’s impression of the bacteria, which start off as rod-like shapes but after they get stuck inside of a crystal they quickly convert, within a matter of weeks, into round, round shape ones, as seen below


There could be lots of reasons why they adopt the round shape. It maybe just for energy conservation. They’re much smaller and they don’t have to expend much energy swimming around as much.

But how do they live. This is a question that biochemists and geo biologists are still trying to figure out.

Researchers do know that there are halophiles, which are any organism that love to live in salt water. So, for example, if Halo files were removed from a salt solution salon and put in regular water they would die instantaneously, they have to live in super, super salty water.

The halophiles, named after the Greek word for “salt-loving”, are extremophiles that thrive in high salt concentrations. While most halophiles are classified into the domain Archaea, there are also bacterial halophiles and some eukaryotic species, such as the alga Dunaliella salina and fungus Wallemia ichthyophaga. Some well-known species give off a red color from carotenoid compounds, notably bacteriorhodopsin. Halophiles can be found in water bodies with salt concentration more than five times greater than that of the ocean, such as the Great Salt Lake in Utah, Owens Lake in California, the Dead Sea, and in evaporation ponds. They are theorized to be a possible candidate for extremophiles living in the salty subsurface water ocean of Jupiter’s Europa and other similar moons.

Halophiles can be photosynthetic i.e., they can get their energy from conversion of sunlight.

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms’ activities.

Lots of sunlight can penetrate through the crystals.

Halophiles can also be chemosynthetic meaning that they can take in chemicals and break them down to releasee energy that they can use to live.

In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydrogen sulfide) or ferrous ions as a source of energy, rather than sunlight, as in photosynthesis. Chemoautotrophs, organisms that obtain carbon from carbon dioxide through chemosynthesis, are phylogenetically diverse, but also groups that include conspicuous or biogeochemically-important taxa include the sulfur-oxidizing gamma and epsilon proteobacteria, the Aquificae, the methanogenic archaea and the neutrophilic iron-oxidizing bacteria.

Many microorganisms in dark regions of the oceans use chemosynthesis to produce biomass from single carbon molecules. Two categories can be distinguished. In the rare sites where hydrogen molecules (H2) are available, the energy available from the reaction between CO2 and H2 (leading to production of methane, CH4) can be large enough to drive the production of biomass. Alternatively, in most oceanic environments, energy for chemosynthesis derives from reactions in which substances such as hydrogen sulfide or ammonia are oxidized. This may occur with or without the presence of oxygen.

It has been hypothesized that anaerobic chemosynthesis may support life below the surface of Mars, Jupiter’s moon Europa, and other planets. Chemosynthesis may have also been the first type of metabolism that evolved on Earth, leading the way for cellular respiration and photosynthesis to develop later.

There are lots of different energy sources for the bacteria trapped in crystals, but photosynthesis and chemosynthesis are the main ones that researchers are looking at, however the bacterial can also consume food that’s been trapped in other parts of the crystal as the fluid inclusions themselves can move around inside the crystal.

Researchers are investigating different environments for evidence of life. Salt lakes are one of them, and they receive a lot of sunlight, but there are lots of places on Earth where there’s not much sunlight.


Above is an image of Professor Celestian in the Boulby mine in March 2020

Boulby Mine is a 200-hectare site located just south-east of the village of Boulby, on the north-east coast of the North York Moors in Loftus, North Yorkshire England.

Because of its depth, Boulby Mine is the site of the Boulby Underground Laboratory 1,100 m below the surface (2800 metre water equivalent).

Work being carried out at the underground laboratory includes the UK Centre for Astrobiology study of extremophile organisms that can survive in a salt-rich environment. The site is also used for testing NASA Mars rovers.

The professor is banging on rocks and looking for crystals that could be good candidates to have bacteria inside them.

The interesting thing about the Boulby mine, is that the salt crystals found there were deposited 250 million years ago. It would be pretty amazing to find bacteria still living in the salt crystals.

The professor spent a week down there.


He found crystals like the one shown above. They had fluid inclusions but there were also clay and other minerals trapped in the crystals as well. These could potentially hold other biochemical signatures or could potentially have food for the bacteria to live on.

He did find bacteria in the 250-million-year-old crystals

There isn’t a microscope video of it yet as he and his team are still processing the data. But they were watching them swimming around on the microscope screen in the lab.

It is quite amazing that the bacteria and the ecosystem can still exist for 250 million years. This is significant as this may be a viable option for looking for life on other planets.

The Boulby samples were taken from almost a mile down below the surface of the Earth and rovers currently can’t get there.

The Boulby samples mean that just because researchers can’t find life on the surface of a planet this doesn’t mean there isn’t life existing below the surface.


So, thinking about Mars, what sort of environments might there be on Mars to support life.

The first Mars missions were trying to find evidence of water

The planet Mars has been explored remotely by spacecraft. Probes sent from Earth, beginning in the late 20th century, have yielded a large increase in knowledge about the Martian system, focused primarily on understanding its geology and habitability potential.

NASA’s Mars Odyssey orbiter entered Mars orbit in 2001. Odyssey’s Gamma Ray Spectrometer detected significant amounts of hydrogen in the upper metre or so of regolith on Mars. This hydrogen is thought to be contained in large deposits of water ice.

In January 2004, the NASA twin Mars Exploration Rovers named Spirit (MER-A) and Opportunity (MER-B) landed on the surface of Mars. Both met and exceeded all their science objectives. Among the most significant scientific returns has been conclusive evidence that liquid water existed at some time in the past at both landing sites.

Phoenix landed on the north polar region of Mars on May 25, 2008. Its robotic arm dug into the Martian soil and the presence of water ice was confirmed on June 20, 2008.

So yes, there is evidence of water and life, as we know it requires water.

We’ve seen that water can be found in crystals and previous NASA missions have found water outside of planet Earth.

If you’re going to look for halophiles, you first need to find salty places.

The following are satellite images of the surface of Mars during its summer. Scrolling through the images some dark streaks start to happen. It looks like water is running down gullies, from bottom right to top left, and then the water slowly starts to evaporate back into the swells.



The first image shows the beginning of the summer and over the following weeks the streaks appear and then disappear. This happens every summer on Mars at many different places.

Scientists think that these are called “reoccurring slope 28” but that’s just a fancy phrase for water leaking out of the rock and getting the soil damp, This is essentially what they think is happening during the summer.

Seasonal flows on warm Martian slopes (also called recurring slope lineae, recurrent slope lineae and RSL) are thought to be salty water flows occurring during the warmest months on Mars, or alternatively, dry grains that “flow” downslope of at least 27 degrees.

The flows are narrow (0.5 to 5 metres) and exhibit relatively dark markings on steep (25° to 40°) slopes, appear and incrementally grow during warm seasons and fade in cold seasons. Liquid brines near the surface have been proposed to explain this activity, or dry granular flows.

image image


During the summer some of the minerals become unstable. There may even be an aquafier somewhere. Some of the places holding the water heat slightly and the water rises to the surface, staining the soil that’s there.

During past ages, there was rain and snow on Mars; especially in the Noachian and early Hesperian epochs. Some moisture entered the ground and formed aquifers. That is, the water went into the ground, seeped down until it reached a formation that would not allow it to penetrate further (such a layer is called impermeable). Water then accumulated forming a saturated layer. Deep aquifers may still exist.

When it gets cold or the environment or the weather changes the staining goes away and this happens every single year in Mars.

Researchers have found salty environments on Mars as well as water but they haven’t found evidence of life, yet. That is the whole goal of the next Mars rover, which was described earlier.

The Perseverance rover and the Ingenuity helicopter drone are due to reach the Jezero crater on Mars on the 18th of February 2021.

Jezero is a crater on Mars located at 18.38°N 77.58°E in the Syrtis Major quadrangle. The diameter of the crater is about 49.0 km. Thought to have once been flooded with water, the crater contains a fan-delta deposit rich in clays. The lake in the crater was present when valley networks were forming on Mars. Besides having a delta, the crater shows point bars and inverted channels. From a study of the delta and channels, it was concluded that the lake inside the crater probably formed during a period when there was continual surface runoff.

In 2007, following the discovery of its ancient lake, the crater was named for Jezero in Bosnia and Herzegovina, one of several eponymous towns in the country.

In November 2020, evidence of boulder fall has been found on the slopes of the delta deposits that the Perseverance rover will explore, on the wall of Jezero crater and on the wall of a small crater (2 km diameter) on the floor of Jezero crater.


Jezero crater map (Green circle: rover’s landing ellipse) (15 July 2020)

Mapping minerals on Mars using CRISM

The Compact Reconnaissance Imaging Spectrometer for Mars is known as CRISM. CRISM uses detectors that see in visible, infrared and near-infrared wavelengths to map the kind of mineral residue that appears where water once existed.

The CRISM instrument team comprises scientists from over ten universities and led by principal investigator Scott Murchie. CRISM was designed, built, and tested by the Johns Hopkins University Applied Physics Laboratory.

Jezero crater is very old and was thought to be flooded about 3.5 billion years ago in Mars’ history.


The image above is a false colour image of the crater. The colours were chosen to indicate what minerals might be present in that area. Perhaps different types of salt minerals mentioned earlier like halites, tolbachites, eriochalcite, thenardite, mirabilite, epsomite and gypsum.

But one thing that is noticeable about the image is there is something that looks very like a stream (top left to right). The stream appeared to empty into a lake with a positive delta structure. On Earth, you only get a delta structure with a river flowing into a lake or sea.

Because of the change in energy from the river rushing in to the stillness of the lake anything that’s being transported by the river just sort of drops out and gets deposited right at that lake-stream interface and forms these deltas.

To the right of the crater there looks like a nice delta formation. This would be a perfect place to look for minerals left behind after evaporation that might have harboured life at some point in time.


The above image shows a delta structure on Earth

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution.

The image of Jezero Crater on Mars, below, has added colour to highlight minerals at the landing site for NASA’s Mars 2020 mission. The green colour represents minerals called carbonates, which are especially good at preserving fossilized life on Earth. Red represents olivine sand eroding out of carbonate-containing rocks. The image was created using data taken by NASA’s Mars Reconnaissance Orbiter and its Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and Context Camera (CTX). The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, led the work to build the CRISM instrument and operates CRISM in coordination with an international team of researchers from universities, government and the private sector. Malin Space Science Systems in San Diego built and operates CTX. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it.



PIA23380: Jezero Crater Minerals

So, Mars 2020 is the next mission. Hopefully sometime late in 2021, if the rover lands safely in February 2021, the collection of real data will provide evidence of life.

Question and answers

1) What is thought to be the most common, common mineral in our solar system?

It could be ice as it is a mineral, it is crystal and it is naturally occurring. However, there are many places that haven’t been investigated. Scientists know from comets that there are many different minerals in space.

A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometres across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times Earth’s diameter, while the tail may stretch beyond one astronomical unit.

The solid, core structure of a comet is known as the nucleus. Cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen carbon dioxide, carbon monoxide, methane, and ammonia.

The surface of the nucleus is generally dry, dusty or rocky, suggesting that the ices are hidden beneath a surface crust several metres thick. In addition to the gases already mentioned, the nuclei contain a variety of organic compounds, which may include methanol, hydrogen cyanide, formaldehyde, ethanol, ethane, and perhaps more complex molecules such as long-chain hydrocarbons and amino acids. In 2009, it was confirmed that the amino acid glycine had been found in the comet dust recovered by NASA’s Stardust mission. In August 2011, a report, based on NASA studies of meteorites found on Earth, was published suggesting DNA and RNA components (adenine, guanine, and related organic molecules) may have been formed on asteroids and comets.

Icy worlds like Neptune and Saturn along with their moons might contain minerals but if they are, we have no idea of what they could be, yet

2) Could bacteria from your research cause a pandemic?

I don’t think so. The halophile bacteria actually explode as soon as they get out of their salty environment. They can’t live in regular environments so it’s highly unlikely that any of the materials collected from Mars will cause problems but precautions are going to be taken so that people don’t interact with them.

3) Why do some bacteria prefer very salty environments.

Well, this particular life form has evolved to live in salty environments such as the salt lakes. It has also evolved to cope with water from the lake constantly evaporating and drying up during the summer and the rains happening in winter.

So, anything able to live in the salt lake would have to adapt to a constantly changing environment. So, these halophiles have found a way to be able to do this. They have found a way to resist those really high concentrations of salt in the water, when the water evaporates but also cope when the salt solution becomes diluted when it rains in winter. It is an evolutionary process that has allowed them to do that.

4) What is the difference between mineralogist and geologist?

Not much. Geology is a big umbrella term and mineralogy is a subdiscipline. A geo biologist will also be considered a geologist.

Geology is an Earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other Earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated Earth system science and planetary science.

Mineralogy is a subject of geology specialising in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.

5) Were the bacteria in the Boulby mine the oldest you’ve seen?

Because of the pandemic we didn’t actually get our samples back from England until a couple weeks ago and I still haven’t had a chance to look at them. They’re probably 250 million years old or so. We will have a better idea of their age after we have done some tests. They could even have come from someplace else. But we really need to figure out if the samples have come from an isolated ecosystem underneath the surface of the earth, for the last 250 million years, or if there’s been mixing of other waters in the area that could contaminated them. We will definitely be making sure.

6) Have the bacteria been breeding in the crystals for the last 250 million years or are they just very long lived?

Once the bacteria get inside the crystal, they become dormant pretty quickly. They still do have some metabolic activity to keep themselves alive. They can do some RNA repair. They use the RNA to repair broken DNA and we don’t know how long they can do this for.

There has been plenty of examples of life living in crystals for hundreds of thousands of years but 250 million years is a really long period of time. It would be amazing to make that discovery.

7) Couldn’t life on other planets have survived on something completely different than water.

It is very possible and that brings up the question of whether there is a different form of life to what we’re used to. We are studying life as we know it. Does this mean there is life as we don’t know it. This is pretty difficult. There are groups of scientists called theoretical evolutionary biologists who are trying to figure out if there is life that doesn’t need water and what these organisms could look like. I can’t answer the question off the top of my head but I know people are thinking about it. So maybe we can get some answers from them.

8) One of the crystals you talked about looked very different when it dried out. If water is added to it would it revert back to its original state.

Mirabilite dries out to form thernardite, but if you just add water to thernardite it would completely dissolve and you’d have to re-crystallize out the mirabilite slowly from the solution.

There is a way to go from thernardite it back to mirabilite without dissolving it but the process involves a really high humid environment. So instead of liquid water you have air with a high concentration of water vapour and the thernardite slowly grows back into mirabilite. This could happen on other moons and planets.

9) Why do halite crystals form cubes.

Crystals cube shapes are down to how atoms come together. The atoms in halite are sodium and chlorine and when they come together, they form little cubic clusters. As more and more sodium and chlorine atoms are added the cubic structure gets bigger until the crystal becomes visible. In fact, all crystal shapes are determined by how the atoms are arranged in space. The diamond cubic crystal structure is a repeating pattern of 8 carbon atoms that certain materials may adopt as they solidify. While the first known example was diamond (in the form when first mined), other elements in group 14 also adopt this structure, including the semiconductors silicon and germanium.

10) Could life forms be based on substances other than carbon, like silicon for instance?

Yes, of course but we don’t have really have examples like that on Earth. So, it’s kind of difficult to do experimental work. But scientists are definitely thinking about what other forms of life could be like if they aren’t carbon based. They are also thinking about how they could detect the non-carbon-based life forms.

If you’re detecting carbon-based life-forms by the chemicals they produce. How could you detect the non-carbon-based ones? Scientists are looking at this.

11) I’m amazed that bacteria can live for 250 million years with no contact with the outside world. Can the DNA of these bacteria, tell us anything about evolution and could these bacteria survive interstellar space on asteroids and seed life on other planets?

If the bacteria are trapped inside of a crystal and the crystal goes flying through space and lands somewhere else it is possible that once the crystal dissolves and turns into a liquid/solution they could be released. It is possible that they could adapt to that environment.

12) There are other heat sources deep down in the Earth. When you first go down the mine it does get colder initially but as you go deeper it actually starts to warm back up. The Earth gets hotter and hotter as you go deeper and sometimes it gets so hot you have to pump in cold air just to keep cool.

13) What is your favourite crystal, and why?

That’s a tough one to answer. So right now, my favourite crystal is a mineral called natrolite. It is a long skinny crystal, but it has all kinds of amazing uses such as chemical catalysis. It can also be used for the clean-up of radioactive waste and it is also useful for drug delivery. Pharmaceutical companies put the drug inside these minerals. The minerals float about in your body and deliver the drug to where it needs to go. It is an amazing compound and it’s just naturally occurring.

Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula Na2Al2Si3O10 • 2H2O.

Needle stone or needle-zeolite are other informal names, alluding to the common acicular habit of the crystals, which are often very slender and are aggregated in divergent tufts. The crystals are frequently epitaxial overgrowths of natrolite, mesolite, and gonnardite in various orders.


Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst. Catalysts are not consumed in the catalysed reaction but can act repeatedly. Often only very small amounts of catalyst are required.

14) Where can you find the oldest crystals in UK

I don’t know. I would have to look it up (not an unreasonable answer as the professor is an American)

15) How do crystals get their names?

Crystals names come from a committee. If I were to find a crystal and I have done this. In fact, the lab here at the museum has one of the most productive labs in the world for discovering new minerals. There are about 100 new minerals discovered every year. Their names sometimes come from the locality of where they’re found.

There’s one, I think called something creedite because it was first described in 1916 from the Creede Quadrangle in Mineral County, Colorado.

Creedite is a calcium aluminium sulfate fluoro hydroxide mineral with formula: Ca3Al2SO4(F,OH)10·2(H2O). Creedite forms colourless to white to purple monoclinic prismatic crystals.


Sometimes crystals are named after people

You can’t name a mineral after yourself because that is against the rules. You can arrange to name the crystal after other people.

16) Do you think that there will be liquid inclusions on Martian halites?

I definitely think so. It would be hard to imagine growing a halite crystal from an evaporating pond that does not have fluids trapped in it. Everyone I’ve seen has at least one minimum, but most of time they are chock full of fluids and they last forever.

17) How long does it take for a crystal to be made naturally?

It depends. The salt crystals can form overnight and you can get really big crystals. You can do an experiment in your own house. You can pour halites or ordinary table salt into a beaker or a jar of hot water until no more will dissolve. Cover the container and you’ll notice that as the water slowly evaporates you get bigger and bigger crystals. This might take a month or so.

If you allow the water to evaporate very fast then you’ll get really small crystals. So how long it takes for the water to leave versus how big the crystals are is directly related to how some other crystals may take millions of years to form.

This large time frame is because of their environment and the quantity of chemicals available for their growth.

There is a whole broad range of timescales for different crystals

18) How do we define life?

I can’t answer that but there is a nice lecture by Charles Cockell called “What is life?”


Charles Cockell FRSE (born 21 May 1967) is a British astrobiologist who is professor of astrobiology in the School of Physics and Astronomy at the University of Edinburgh and director of the UK Centre for Astrobiology. He was previously Professor of Geomicrobiology with the Open University and a microbiologist with the British Antarctic Survey, Cambridge, UK. His scientific interests have focused on astrobiology, geomicrobiology and life in extreme environments. He has published over 300 scientific papers and books in these areas.[3] He has contributed to plans for the human exploration of Mars. For example, he led the design study Project Boreas, which planned and designed a research station for the Martian polar ice caps. He was the first chair of the Astrobiology Society of Britain.

19) Why do the crystal names end in “ite”

The suffix “ite” is derived from the Greek word lithos (from its adjectival form -ites), meaning rock or stone.

Most mineral names end in “ite” but they don’t have to. It’s just a tradition. So, calcite ends in “ite” but olivine doesn’t, and neither does peridot


Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3).


The mineral olivine (is a magnesium iron silicate with the formula (Mg2+, Fe2+)2SiO4.

Peridotite is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene.


20) Where are most crystals found?

Crystals are found everywhere. They are found in the human body. Our teeth and bones are made out of crystals. There are crystals in our ears to help keep our balance. There are crystals in pens and pencils and they are truly found everywhere.

21) Do you think live bacteria will be found in crystals on Mars?

I am hopeful. I am an optimist, but there are people who are sceptical. We won’t know until we look. I think the best place to look is probably going to be inside the salt crystals.

22) So would finding a substance, such as a beta carotene be conclusive evidence of life and are there any non-biological mechanisms which might produce it.

We have thought about this quite a bit. There probably is some sort of non-biological mechanisms for making beta carotene, but in the natural environment on Earth the beta carotene is only produced by bacteria or by other living things. That’s one reason why we’re so eager to look inside the salt crystals for beta carotene or beta carotene like compounds because that would be pretty much conclusive evidence for life. Living things produce beta carotene

23) If you do find life is it ethical to keep investigating or should it be left to involve in its own way.

I think based on our current standard of ethics in science, there is a need to study life. Maybe take only small amounts of it away from the environment so its absence wouldn’t impact the overall evolutionary processes that are happening in that environment. But people have different opinions on this. I work at a natural history museum where many people’s jobs involve going out and collecting living organisms and bringing them back into the collection, but they do so as ethically as they possibly can.

If there’s this one bird out there and it is the only one in existence. You don’t want to go out and grab it just to say that you have this fancy bird because that would be unethical. But if you go out and there are 5 million birds then it’s much easier to justify collecting a few specimens for the museum to study over a long period of time and sharing the information with other scientist in the world so they don’t have to go out and collect their own birds. With minerals and bacteria and there’s less of a less of an issue. But we definitely think about the issues.

24) Are the bacteria that you found in the 250-million-year-old crystals, in the mine, different from other known bacteria or are they very much the same?

We don’t know yet. We are doing the DNA sequencing as fast as we possibly can. I’m not doing the sequencing, my colleagues at JPL NASA are doing them. But it will be really important because if they are significantly different it shows that they’ve been separated from the rest of the surface environments for a long period of time. And there are ways of looking at evolutionary pathways of bacteria and seeing whether they have diverged and potentially how long ago that could have happened. So right now, we don’t know. We’ve only just got the samples back a couple weeks ago. It should take another month or so, but with all the labs being shut down because of the pandemic. Who knows when we will actually find out, hopefully by the end of the year?

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