Once the rock samples were drilled, Curiosity's robotic arm delivered the rock powder to the Sample Analysis on Mars (SAM) instrument, where it was used for a variety of chemical analyses, including the geochronology—or rock dating—techniques.

One technique, potassium-argon dating, determines the age of a rock sample by measuring how much argon gas it contains.

In a way this field, called geochronology, is some of the purest detective work earth scientists do.

There are two basic approaches: relative age dating, and absolute age dating.

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.

Now, for the first time, researchers have successfully determined the age of a Martian rock—with experiments performed on Mars.

Scientists can use certain types of fossils referred to as index fossils to assist in relative dating via correlation.

Index fossils are fossils that are known to only occur within a very specific age range.

Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type.

those that form during chemical reactions without breaking down).

The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.

Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.

Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old.