Planet hunting may take a back seat in NASA's new budget.

"Funding for the [Terrestrial Planet Finder] missions was drastically cut," said James Kasting, professor of geosciences and meteorology, Kasting is co-chair for the science and technology definition team for NASA's Terrestrial Planet Finder-Coronagraph.

The TPF-C mission will use visible light, while the TPF-Interferometer will use infrared light to search distant planets for biomarker gases -- gases that would indicate the presence of life, Kasting said.

"The first mission would have flown in 10 to 11 years," he said. Now the launch date will have to be pushed back.

The search for planets around distant stars is directed to the habitable zone -- the region around a star where an Earth-like planet could maintain liquid water, said James Kasting.

The habitable zone around a star is the area where life is most likely to form.

As a star ages, it gets brighter and causes the habitable zone to shift outward over a long period of time, he added.However, not all habitable places are located inside this region, Kasting said. Europa, one of the moons that orbits Jupiter, could be an example of this, he said, because the moon is internally heated.

Kasting spoke about multiple possibilities for the boundaries of the habitable zone.

He used this solar system as an example, where any planet that formed inside a distance of .95 Astronomical Units (1 AU is the distance from the Earth to the Sun), a planet would begin to experience a runaway greenhouse effect. Venus is the prime example.

In the case of Mars, the planet formed just inside the habitable zone, but did not have enough internal volcanic activity to retain heat, he said.

Depending on what factors are taken into account and if the view is optimistic or pessimistic, the outer edge of the habitable zone could range from 1.01 AU to 1.8 AU.

Over 70 people attended Kasting's presentation on "Habitable Zones Around Stars and the Search for Extraterrestrial Life" on Thursday in Osmond Lab.

Currently, over 100 planets have been discovered, with approximately 20 falling within the habitable zone, Kastings said. Most of those planets could not be habitable because they are similar to Jupiter, but the moons might be.