Seth Shostak Quotes

Mars was this water-based planet, and we know there was stable water on the surface for a long time, which is critical for life having a chance to develop.

Mars is much closer to the characteristics of Earth. It has a fall, winter, summer and spring. North Pole, South Pole, mountains and lots of ice. No one is going to live on Venus; no one is going to live on Jupiter.

Earth as an ecosystem stands out in the all of the universe. There's no place that we know about that can support life as we know it, not even our sister planet, Mars, where we might set up housekeeping someday, but at great effort and trouble we have to recreate the things we take for granted here.

The earth's crust has not yet stopped heaving and plunging under our feet. Mountain ranges are still being thrust up on the horizon. Granites are still growing under the continental masses. Nor has the organic world ceased to produce new buds at the tips of its countless branches.

The reason you see so many volcanoes on Venus is partly due to the fact that there's virtually no erosion there. So on Venus, you're seeing features, some of which are hundreds of millions of years old on the surface. On Earth, we do not see any surface features nearly that old - you only see much more recent features.

We may confidently come to the conclusion, that the forces which slowly and by little starts uplift continents, and that those which at successive periods pour forth volcanic matter from open orifices, are identical.

Now we notice that Mars doesn't have any atmosphere either and won't support life. In spite of the fact that it turns green and red and purple with the seasons, it doesn't support life.

Thus it cannot be denied that the masses which today form our highest mountains were originally in a liquid state; for a long time they were covered by waters which did not sustain any life.

Many different planets are many different distances from their host star; we find ourselves at this distance because if we were closer or farther away, the temperature would be hotter or colder, eliminating liquid water, an essential ingredient for our survival.

During the Tertiary period the whole valley of Mexico was one great lake.

If you could drive straight down, into a tunnel bored through the crust of the planet, you'd hit this molten mess in about an hour. It's called the asthenosphere - a sluggish sea, several hundred miles thick, on which floats the Earth's cool epidermis - the so-called tectonic plates.

Unfortunately, we haven't found many very old rocks on Earth because our planet's surface is constantly renewed by plate tectonics, coupled with erosion.

Stars, of course, are too hot to support life, so wherever life might exist in the universe, it has to be on planets or moons that are warmed, but not incinerated, by the stars they travel around.

Plate tectonics is not all havoc and destruction. The slow movement of continents and ocean floors recycles carbon dioxide dissolved in the oceans back into the atmosphere. Without this slow speed carbon cycle, Earth's temperatures would cool dozens of degrees below your comfort zone.

The traces of upheavals become more impressive when one moves a little higher, when one gets even closer to the foot of the great mountain ranges. There are still plenty of shell layers. We notice them, even thicker and more solid ones.

If we strike a line to the N.W. from Sydney to Wellington Valley, we shall find that little change takes place in the geological features of the country.

The usual metric for whether a planet is habitable or not is to ascertain whether liquid water could exist on its surface. Most worlds will either be too cold, too hot or of a type (like Jupiter) that may have no solid surface and be swaddled in noxious gases.

In days gone by, scientists would speak solemnly about our solar system's 'habitable zone' - a theoretical region extending from Venus to Mars, but perhaps not encompassing either, where a planet would be the right temperature to have liquid water on its surface.

I am not sufficiently conceited to think that my sun is the only one with a family of planets and, therefore, that our little earth is unique. Once we admit that the other stars probably also have planets, at any rate a goodly proportion of them, it is more than likely that a large fraction of these will be the right size to keep on their surface water and, possibly, an atmosphere of some sort; and, furthermore, at the proper distance from their parent sun, to maintain a suitable temperature.

A lot of the science fiction that I grew up reading was written when we still thought that Venus might be an oceanic planet.

It will be a long time, if ever, before we get to study Earth-like planets orbiting around other stars, so really, the study of Venus and Mars is the best opportunity that we have, and can imagine having anytime in the future, to understand the evolution of Earth-like planets.

Pluto is still active four and a half billion years into its history. It was expected that small planets like Pluto would cool off long ago and not still be showing geological activity. Pluto is, in fact, showing numerous examples of geological activity on a massive scale across the planet.

The story seems to be that almost every star has a planetary system... and, also, the definition of 'habitable zone' has expanded. In our system, it used to be that only Mars and Earth were potentially habitable. Now we've got an ocean on Europa... Titan.

Every observation that we make, every mission that we send to various places in the solar system is just taking us one step further to finding that truly habitable environment, a water-rich environment.

Like a mountain that's growing.