The majority of the time fossils are dated using relative dating techniques.Using relative dating the fossil is compared to something for which an age is already known.But, how can we determine how old a rock formation is, if it hasn’t previously been dated?
Now, for the first time, researchers have successfully determined the age of a Martian rock—with experiments performed on Mars.
The work, led by geochemist Ken Farley of the California Institute of Technology (Caltech), could not only help in understanding the geologic history of Mars but also aid in the search for evidence of ancient life on the planet.
It is based on the fact that some of the radioactive isotope of Potassium, Potassium-40 (K-40) ,decays to the gas Argon as Argon-40 (Ar-40).
By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined. Potassium (K) is one of the most abundant elements in the Earth's crust (2.4% by mass).
Potassium-Argon dating is the only viable technique for dating very old archaeological materials.
Geologists have used this method to date rocks as much as 4 billion years old.
Index fossils are fossils that are known to only occur within a very specific age range.
Although researchers have determined the ages of rocks from other planetary bodies, the actual experiments—like analyzing meteorites and moon rocks—have always been done on Earth.
One out of every 10,000 Potassium atoms is radioactive Potassium-40 (K-40).
This each has 19 protons and 21 neutrons in their nucleus.
Results on a chondrite meteorite specimen of the Forest City Fall, Iowa, confirm to a remarkable degree earlier data on another specimen from another laboratory and thus confirm a potassium-argon age close to 4500 m.y.