The more we know, the simpler things are!!

There is a new, "inexpensive way of predicting what extrasolar planets (otherwise known as exo-planets) are made of, simply by looking at the chemical composition of their host stars..."

"If a distant star contains high levels of iron, for instance, chances are that inner, rocky planets circling that star will also contain similar levels of iron..."

More details: here (PDF).

According to Dr Charles H. Lineweaver:
"Estimating the habitability of nearby planets is one of the most important priorities in astronomy.
Small variations in the abundances of critical elements (e.g. C, O, Mg, Si, S and radioactive isotopes) strongly affect habitability. In our preliminary efforts to make quantitative estimates of
the characteristics of Earth-like planets orbiting nearby stars and determine their habitability, we will proceed as follows:

1. determine the elemental fractionation depletion patterns that produced the terrestrial planets of our Solar System starting from solar composition material

2. determine the range of stellar elemental abundances from comprehensive new stellar
spectroscopic surveys and compare the abundances to solar values

3. estimate the chemical composition of terrestrial planets around nearby stars based on the depletion pattern of 1. and the stellar abundances of 2. above

4. classify terrestrial planets based on the estimates of the ranges over which the most important elemental abundances of terrestrial planets can vary

5. develop tighter links between bulk composition and habitability by studying these links on Earth."