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What, exactly, is a plant made of? Scientists have a good understanding of the essential nutrients plants need to grow. But what plants need and what they contain are not necessarily the same.

As plants draw water and nutrients through their roots, they can also absorb other elements from their surroundings. Those elements become incorporated into plant tissues—meaning what's in the ground can help shape what's in the plant.

That becomes especially important when the ground isn't on Earth.

Researchers studying the possibility of growing plants on the moon and Mars want to understand what could happen when their roots encounter regolith, the rocky material rich in metals that covers their surfaces.…