Can humans build structures on other planets? Maybe it could be as easy as giving blood.

Given the expense and difficulty of getting building materials to places like the moon or Mars, the idea of construction is tricky at best.

A new study suggests some surprising materials that could make the task much easier: astronauts’ blood, urine, or even tears.

In a paper in Materials Today Bio, researchers explore a proposed way to add astronauts’ own bodily fluids to another planet’s soil. The resulting material would be similar to concrete — but could be reinforced to be even stronger.

The formula relies on combining human serum albumin, the most abundant protein in blood plasma, with water and the dust and rock on other planets. They call the resulting material, which is similar to concrete, AstroCrete.

When the researchers added urea — a substance found in urine, sweat and tears — to the mixture, it increased its compressive strength threefold, making it much stronger than concrete.

The paper lays out the method and suggests ways to harvest the needed compounds and use them on a hypothetical lunar or Martian base. The compound could be used to create bricks or act as a mortar that binds existing rocks together, helping astronauts create much-needed shelters against the sun’s radiation.

The scientists admit the feasibility and health effects of the method would need “significant further investigation,” but they suggest a single astronaut could fuel the creation of the equivalent of a single clay brick a month with their blood plasma alone. Over the course of a mission on Mars, they write, each astronaut “could produce enough additional habitat space to support another astronaut, potentially allowing the steady expansion of an early Martian colony.”