Astronomers find Al-26, a radioactive form of aluminum, can heat up and dry out the large boulders (called planetesimals) that collide to form planets. More Al-26 leads to a dry, desiccated planet, while a lack of Al-26 allows water worlds to form, some of which have up to 50% water by mass.

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Astronomers find Al-26, a radioactive form of aluminum, can heat up and dry out the large boulders (called planetesimals) that collide to form planets. More Al-26 leads to a dry, desiccated planet, while a lack of Al-26 allows water worlds to form, some of which have up to 50% water by mass.