Animated Map: Where to Find Water on Mars
Animation: New Water Map of Mars
The hunt for water on Mars has always been a point of interest for researchers.
Earth has life almost everywhere water exists. Water is an ideal target for finding lifeforms, like microbes, that may exist on other planets.
And if Mars is to become a future home, knowing where water exists will be necessary for our survival.
Both NASA and the European Space Agency (ESA) have special instruments searching for water on the red planet. After 10 years of in-depth investigation, their latest findings suggest a new “water map” for Mars.
Where Did the Water Go?
Many people know Mars as a dry and dusty planet, but it hasn’t always been that way.
Approximately 4.1 to 3.8 billion years ago, Mars had a massive ocean called Oceanus Borealis. It dominated the northern hemisphere of the planet. Specific planetary conditions at that time let water exist on its surface. Changes in temperature, climate, and geology over the years gradually pushed water out to the atmosphere or into the ground.
Up to 99% of this ocean water is trapped within the planet’s crust, locked within special rocks called hydrous minerals.
Hydrous minerals are essentially rocks that have water (or its two main elements, hydrogen and oxygen), incorporated into their chemical structure.
There are four main classes of hydrous minerals: silicates, sulfates, silicas, and carbonates. While these minerals look pretty similar to the naked eye, their chemical compositions and structural arrangements vary. They are detectable by sophisticated equipment and can tell scientists how water geologically changes over time.
The new water map of Mars actually highlights the location of these hydrous minerals. It is a geological map of the rocks that are holding what remains of Mars’s ancient ocean.
Other Sources of Water on Mars
Despite being a “graveyard” for the bulk of the planet’s ocean, hydrous minerals are not the only source of water on Mars.
Water ice is present at both of Mars’s poles. The northern polar ice cap contains the only visible water on the planet, while the southern pole covers its water with a frozen carbon-dioxide cap.
In 2020, radar analyses suggested the presence of liquid water, potentially part of a network of underground saltwater lakes, close to the southern pole. In 2022, new evidence for this liquid water suggested that the planet may still be geothermally active.
More frozen water may be locked away in the deep subsurface, far below what current surveying equipment is able to inspect.
Mapping Out the Next Missions
The new water map is highlighting areas of interest for future exploration on Mars.
There is a small chance that hydrous minerals may be actively forming near water sources. Finding where they co-exist with known areas of buried frozen water provides possible opportunities for extracting water.
ESA’s Rosalind Franklin Rover will land in Oxia Planum, a region rich in hydrous clays, to investigate how water shaped the region and whether life once began on Mars.
Many more investigations and studies are developing, but for now, scientists are just getting their toes wet as they explore what hydrous minerals can tell us of Mars’s watery past.
Ranked: Biotoxins in Nature, by Lethal Dose
The world can be a poisonous place. We look at a number of different biotoxins found in the natural world and rank their toxicity.
Biotoxins: Poisons of the Natural World
Biotoxins are harmful substances that come from living organisms.
They can take many forms, from the venom of a snake or spider to the neurotoxins produced by certain types of algae or microbes.
In the infographic above, we look at some common biotoxins in the natural world and rank them based on how deadly they are to an average 70 kg (154 lb) human being.
Ranking Biotoxins on a Toxic Scale
A basic concept in toxicology is that “only the dose makes the poison”. Everyday harmless substances like water have the potential to be lethal when consumed in large enough concentrations. Measuring a lethal dosage is very difficult.
First, living things are complex: factors like size, diet, biochemistry, and genetics vary across species. This makes it difficult to qualify toxicity in a universal way.
Second, individual factors like age or sex can also affect how deadly a substance is. This is why children have different doses for medications than adults.
Third, how a poison is taken into the body (orally, intravenously, dermally, etc.) can also impact its deadliness.
As a result, there are many ways to measure and rank toxicity, depending on what substance or organism is under investigation. Median lethal dose (LD50) is one common way for measuring toxicity. LD50 is the dose of a substance that kills 50% of a test population of animals. It is commonly reported as mass of substance per unit of body weight (mg/kg or g/kg). In the graphic above, we curate LD50 data of some select biotoxins found in nature and present them on a scale of logarithmic LD50 values.
What’s surprising is just how potent some toxins can be.
Bits and Bites about Biotoxins
While one would think that biotoxins are avoided at all costs by humans, the reality is more complicated. Here are some interesting facts about biotoxins present in nature, and our unusual relationships with the organisms that create them:
1. Fungi and molds make poisons called mycotoxins
Mycotoxins are a global problem. They affect crops from many countries, and can cause significant economic losses for farmers and food producers.
2. Phytotoxins can defend plants…and attack cancer
Plants use phytotoxins to defend themselves other organisms, like humans. Urushiol, for example, is the main toxic component in the leaves of poison ivy, poison oak, and sumac. But the Pacific yew tree produces taxol that’s valuable in chemotherapy treatments.
3. Fire salamander toxin is an ingredient in Slovenian whisky
Though not widely available, some whisky makers in Slovenia use samandarine from the fire salamander to create a psychedelic alcohol.
4. Ciguatoxins exist in the guts of reef fish
Very unique species of bacteria living in the digestive tract of reef fishes make ciguatoxin. They transmit this poison to other organisms when the host fish is eaten.
5. Pufferfish are deadly, but also delicious
Pufferfish contain tetrodotoxin, a potent neurotoxin in their ovaries, liver, and skin called tetrodotoxin. Despite being a delicacy in many countries around the world, it has a lot of strict regulations because of its ability to kill people. In Japan, for example, only specially licensed chefs can prepare pufferfish for consumption.
6. Batrachotoxin is lethal to the touch
The skin of some poison dart frogs secretes a deadly substance called batrachotoxin. It is so potent that simply touching the poison can be fatal. Indigenous people of Central and South America used batrachotoxin to poison the tips of hunting weapons for centuries.
7. Botox contains the most deadly biotoxin known
Commercial botox uses an extremely small amount of biotoxin from a microbe called Clostridium botulinum. It paralyzes the muscles, preventing contraction (i.e. wrinkling). It is the deadliest known biotoxin on Earth. One gram of botulinum toxin can kill up to one million people.
Caveats of Measuring and Reporting Biotoxicity
While we use LD50 data to rank biotoxicity, it isn’t an exact science. There is room for improvement.
For starters, no LD50 data exists for humans. That means data from other organisms has to be converted to apply to humans. There is a lot of contention amongst scientific communities about how accurate this is.
There has also been an increasing effort to move to new methods of measuring toxicity that are not harmful to animals. Several countries, including the UK, have taken steps to ban the oral LD50, and the Organisation for Economic Co-operation and Development (OECD) abolished the requirement for the oral test in 2001.
Now, new ways of evaluating toxicity are under investigation, like cell-based screening methods.
Correction: Water was mislabeled on a previous version of the infographic. Full sources here
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