We have rocks from the Moon (brought back), meteorites, and rocks that we know came from Mars.We can then use radioactive age dating in order to date the ages of the surfaces (when the rocks first formed, i.e. We also have meteorites from asteroids and can date them, too.
These differing atoms are called isotopes and they are represented by the sum of protons and neutrons in the nucleus. Carbon has 6 protons in its nucleus, but the number of neutrons its nucleus can host range from 6 to 8.
We thus have three different isotopes of carbon: Carbon-12 with 6 protons and 6 neutrons in the nucleus, Carbon-13 with 6 protons and 7 neutrons in the nucleus, Carbon-14 with 6 protons and 8 neutrons in the nucleus.
We have an activity in one of the PSI workshops "Exploring the Terrestrial Planets," that deals with this topic.
So, you can use the radioactive elements to measure the age of rocks and minerals. Their useful range is from about 1/10 their half-life (the time it takes for half of the radioactive element/isotope-- the parent, to convert into a non-radioactive element/isotope-- the daughter) to 10 times their half-life. You can use this to measure the age of a rock from about 128 million years to more than 10 billion years (the Solar System is 4.56 billion years old).
Carbon is unreactive with a number of common lab substances: sulfuric acid, hydrochloric acid, chlorine, or any of the alkalis.
It does burn in oxygen, and if you can pass the combusted gas through limewater, the carbon dioxide will turn the limewater milky by producing calcium carbonate.
Once the half life of an isotope and its decay path are known, it is possible to use the radioactive decay for dating the substance (rock) it belongs to, by measuring the amount of parent and daughter contained in the sample.
An important point is that we must have an idea of how much of the daughter isotope was in the sample before the decay started.
This decay, or loss of energy, results in an atom (element) of one type, called the parent nuclide transforming to an atom of a different type (another element or another isotope of the same element), named the daughter nuclide.