Imagine a world, a world several hundreds of light-years away which humans have promptly colonised. These interstellar pioneers land on the mysterious planet which they call home, only for them to see creatures having- foamy scars? Thinking, "what causes this chemical reaction"?

Some parameters

-The blood needs to be mostly hemoglobin-based

-The wound has to stop bleeding in 10 minutes or less because of the foam

-Has to be biologically possible and plausible to produce

-Has to leave a permanent scar, doesn't necessarily have to regrow into skin


It would also be much appreciated if the foam has a texture similar to that of silicone.

Thanks in advance!

  • $\begingroup$ Does the scar have to be made of the foam, or can the scar be a byproduct of the foam and something else, say maybe sand? $\endgroup$ Sep 11, 2021 at 19:28
  • $\begingroup$ Both are fine, altough only foam would be preferred. $\endgroup$
    – Explunky
    Sep 11, 2021 at 20:04
  • $\begingroup$ Hello there oxigenated water. Oxigenated water is a liquid. Its formula is H2O2. When you apply it on an injury, it begins to foam. When it does that, DO NOT WASH OFF THE FOAM. That foam is applying pressure on the injury and preventing the loss of blood. Use only for small-medium superficial injuries. $\endgroup$ Sep 13, 2021 at 7:39

2 Answers 2


Peroxidase and hydrogen peroxide:

This is alien biology, so anything IS possible. But why not stick to what we know?

The aliens are encrusted in a thick biological coating filled with bacteria. The aliens get a fair amount of protection from this, but when they are actually penetrated, the bacteria are very dangerous for causing infections. They have an under-layer that specializes in sealing up this wound rapidly, but that traps bacteria. The response? They biologically produce hydrogen peroxide, which fills the rapidly-forming clot with a foam of oxygen toxic to the bacteria. So as the clot forms, millions of tiny bubbles of oxygen kill the bacteria that would otherwise be trapped in the rapidly sealing wound.


DWKraus has an excellent suggestion, but it does not explain the hardened scar formation.

A bit of biological engineering, however, suffices to explain the hardened rubber scars.

Latex is a natural compound produced by many plants, and it is used as a defensive coating against insects, infections and bacteria. However, it is a liquid.

One more step is needed.

Coagulating latex into rubber, using a biological process.

The milky fluid obtained from tapped rubber trees is called latex. It consists of an aqueous suspension of colloidal rubber particles.

Each rubber particle is made up of rubber polymers covered by a layer of protein membrane.

Negative charges are found on the surface of the membrane, making each rubber particle negatively charged. The negatively-charged rubber particles repel each other, preventing themselves from combining and coagulating.

Acids such as methanoic acid (forfnic acid) are added to make the latex coagulate.

Hydrogen ions from the acid neutralise the negative charges on the surface of the membrane. A neutral rubber particle is formed.

When these neutral particles collide with each other, their outer membrane layers break up. The rubber polymers are set free.

The rubber polymers start to coagulate by combining together to form large lumps of rubber polymers which then precipitate out of the latex solution.

Latex can still coagulate if acids are not added. Normally, the latex will coagulate if left overnight.

Bacteria from the air slowly attack the protein on the membrane to produce lactic acid. Ionisation of the lactic acid produces hydrogen ions. The hydrogen ions neutralise the negative charges to form neutral rubber particles, allowing coagulation to occur.

Alkalis such as ammonia solution are added to latex to prevent coagulation.

The hydroxide ions from alkali neutralise hydrogen ions produced by lactic acid as a result of bacterial attack on protein.

Because there are no hydrogen ions to neutralise the negative charges on the rubber particles, they remain negatively charged and hence cannot combine and coagulate.

So, the hydrogen peroxide and catalyse enzyme create the oxygen and water foam.

Enzymes are special protein molecules that speed up chemical reactions. But why should liver contain an enzyme that helps degrade hydrogen peroxide? Because hydrogen peroxide actually forms as a product of metabolism and can do some nasty things. It can break apart to yield hydroxyl radicals that attack important biochemicals like proteins and DNA. To protect itself, the body makes catalase, the enzyme that decomposes hydrogen peroxide before it can form hydroxyl radicals.

Actually, the formation of hydrogen peroxide in cells is an attempt by the body to protect itself from an even more dangerous substance, superoxide.

Oxygen is a double-edged sword. We can’t live without it, but it also hastens our demise by playing a role in the aging process. Here’s what happens. Electrons are the “glue” that hold atoms together in molecules, and all sorts of electron transfers occur between molecules when they engage in the numerous chemical reactions that go on in our body all the time. Sometimes during these reactions an electron is transferred to oxygen, converting it into a highly reactive “superoxide” ion that attacks and rips other molecules apart.

But we have evolved a defence system, in this case an enzyme called “superoxide dismutase” that gets rid of superoxide by converting it into hydrogen peroxide, which although potentially dangerous, is less dangerous than superoxide. Still, it does present a risk and this is where catalase enters the picture. It breaks the peroxide down into oxygen and water. And that is why hydrogen peroxide foams when poured onto liver.

The hemoglobin link is explained by

Hemoglobin can attenuate hydrogen peroxide-induced oxidative stress by acting as an antioxidative peroxidase

Hemoglobin is considered a potentially toxic molecule when released from erythrocytes during hemolysis, inflammation, or tissue injury. The mechanisms of toxicity involve reduced nitric oxide bioavailability and oxidative processes both occurring at the heme prosthetic groups. When the endogenous oxidant H(2)O(2) reacts with Hb, transient radicals are generated during the peroxidative consumption of H(2)O(2). If not neutralized, these radicals can lead to tissue toxicity. The net biologic effect of extracellular Hb in an H(2)O(2)-rich environment will therefore be determined by the balance of H(2)O(2) decomposition (potential protective effect) and radical generation (potential damaging effect). Here we show that Hb can protect different cell types from H(2)O(2)-mediated cell death and the associated depletion of intracellular glutathione and ATP. Importantly, Hb blunts the transcriptional oxidative-stress response induced by H(2)O(2) in human vascular smooth muscle cells (VSMCs). Based on spectrophotometric and quantitative mass spectrometry analysis, we suggested a novel mechanism in which Hb redox-cycles H(2)O(2) and simultaneously internalizes the radical burden, with irreversible structural globin changes starting with specific amino acid oxidation involving the heme proximate betaCys93 and ultimately ending with protein precipitation. Our results suggest that complex interactions determine whether extracellular Hb, under certain circumstances, acts a protective or a damaging factor during peroxidative stress conditions.

This foam mixes with the latex, also produced as a defense mechanism. Add in peroxidase, and get even more foam. This latex foam coagulates, perhaps in the presence of bacteria. The added benefit of the hydrogen from hydrogen peroxide is a bonus, enhancing the vulcanization of the rubber. The coagulated latex remains as a rubber-like scar, covering the wound and further protecting it.

A completely plausible scenario based on biological processes that are known in Earth's biology, combined in a unique rubber-scar-forming scenario.

In fact, it makes one wonder why nature has not already found the technique.

  • $\begingroup$ A good suggestion I will probably use, but could you give a brief summary of the processes, because I don't quite get it yet. For example: 1. Hydrogen peroxide and catalase is released from the blood 2. The hydrogen peroxide mixes with the catalase and releases a foamy substance 3. Peroxidase is released after a minute or so 4. Latex is mixed with the foam 5. The latex coagulates into rubber. This is what I interpretated it as, please correct me if something is wrong or if you want to add more information. $\endgroup$
    – Explunky
    Sep 12, 2021 at 19:49
  • 1
    $\begingroup$ Since the entire process does not yet exist, and is purely hypothetical, you can fashion it any way your plot demands. You are not describing a real-life scenario, you are describing your onw scenario based on several individual real life processes. The more detail you go into on a side issue in your story, the more you lose focus on the main plot. Better to handwave the minute details than get lost in them. The process that you suggest is realistic enough for anyone without a biology doctorate. $\endgroup$ Sep 12, 2021 at 23:46
  • 1
    $\begingroup$ For instance if you used the more technical term 'vulcanize' instead of 'coagulates' you risk taking flack from some reader hung up over the more common industrial process for vulcanizing (solidifying) rubber in commercial quantities, insisting that it is too technically complex to be done in nature. Know when to fold, and when to hold. $\endgroup$ Sep 12, 2021 at 23:50
  • 1
    $\begingroup$ Recall that latex is known to be produced only by plants, and blood is only present in mammals, so you are positing an alien crossover between plant and animal. $\endgroup$ Sep 12, 2021 at 23:57

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .