Calcium-41 for Radiometric Dating

• 22 May 2023

Why in News?

Scientists have suggested using Calcium-41 for Radiometric Dating as an alternative to Carbon-14 for determining the age of fossilized bones and rocks.

• They have suggested a technique called Atom-Trap Trace Analysis (ATTA) as a solution, because ATTA is sensitive enough to spot Calcium-41, which is a rare isotope.

What is Calcium-41 and ATTA?

• Calcium-41:
  • Calcium-41 is a rare long-lived radioisotope of calcium with a half-life of 99,400 years.
  • Calcium-41 is produced in the Earth's crust when cosmic rays from space collide with calcium atoms in soil or rocks.
  • This isotope has the potential to be employed in dating methods for objects that are older than what can be accurately determined using carbon-14 dating.
• ATTA:
  • It is based on laser manipulation and detection of neutral atoms.
  • The sample is vaporized, and the atoms are laser-cooled and loaded into a light and magnetic field cage.
  • By tuning the laser’s frequency, Calcium-41 atoms can be detected through electron transitions.
    • Electron transition: In an atom, an electron in one orbital can transition to the next if it’s given a specific amount of energy; then it jumps back by releasing that energy.
  • The researchers reported being able to spot one calcium-41 atom in every 10¹⁶ calcium atoms with 12% precision in seawater.
    • It is selective and avoids confusion with potassium-41 atoms.
• Applications of ATTA:
  • The successful application of a calcium isotope opens the possibility of extension to other metal isotopes.
    • ATTA can be adapted to study other isotopes, such as argon-39, krypton-81, and krypton-85.
  • In warmer climates, glaciers retreat and allow rock below to accumulate calcium-41. In colder climates, glaciers advance and block the calcium-41 from reaching the rock. This way, scientists hope to use ATTA to study how long some rock has been covered by ice.

What is Radiometric Dating?

• About:
  • Radiometric dating is a method used to determine the age of rocks, minerals, and fossils based on the decay of radioactive isotopes.
  • It relies on the principle that certain isotopes of elements are unstable and spontaneously decay over time into more stable forms. The rate of decay is measured by the half-life, which is the time it takes for half of the parent isotope to decay into the daughter isotope.
  • Different isotopes have different half-lives, which makes them useful for dating different time ranges.
    • For example, carbon-14 dating is effective for dating organic materials up to about 50,000 years old. When an organic entity is alive, its body keeps absorbing and losing carbon-14 atoms. When it dies, this process stops and the extant carbon-14 starts to decay away.
    • Using the difference between the relative abundance of these atoms in the body and the number that should’ve been there, researchers can estimate when the entity died.
• Limitations with Carbon-14:
  • Carbon-14 is an unstable and weakly radioactive isotope of carbon. It has a half-life of 5,700 years and is used to estimate the age of carbon-based materials.
  • Carbon dating using Carbon-14 is limited to objects up to 50,000 years old due to carbon-14's 5,700-year half-life.

Source: TH