Some recent selections from the SPACE.com mailbag, on alien intelligence and more.

Astronomer Guillermo Gonzalez responds to recent letters about his opinion piece "Alien Intelligence? Think again."

To the Editor:

In response to the letters to the editor about my opinion piece, I'd like first to point out that my discussion was about advanced complex life (i.e. mammals and other large critters), not simple life. One cannot calculate the probability of the existence of simple life from the unique example of the Earth, because of the obvious self-selection bias. What about Mars? It probably had liquid water on its surface for a while and it was probably seeded with Earth microbes during the tail end of the early heavy bombardment. Yet even with the most Earth-like environment in the solar system, the conditions on Mars have been too harsh even for simple life to keep a foothold.

A recent opinion piece by Peter Glaser advocated space solar power. A reader is skeptical. (Also, see some earlier letters on the subject.)

To the Editor:

Solar Space Power (SSP) is without a doubt, a romantic technology.  But SSP is also very impractical too!  In theory, we could erect huge solar panel farms in low Earth orbit (LEO), or the surface of the moon. With these great space farms we could convert the free energy from the sun and beam it down in the form of microwaves.

In practice, the feasibility of such a system is entirely unrealistic based on current launch costs. When one calculates the cost of moving one kilogram (2.2 pounds) of mass into space, and figures what the total mass of such a SSP station would weigh, this technology becomes prohibitively expensive to move from the ground up. For this solar power to be competitive in today’s market, many changes need to be made. The most significant change will be the cost to transfer a mass from Earth into space. The cost will need to drop an enormous order of magnitude to become feasible. At the moment, there are no companies, either private or governmental, that can deliver the type of payloads at such a low cost. Although current technology will be able to build such a power station in space, we will need solar power panels to become more efficient than they currently are. This factor is directly proportional to the size the station will need to be.

There are several other factors that need to be accounted for, most notably, who will still make heavy-lift launch vehicles to move such masses into space? The great days of the Apollo era are long gone and all we have is a lousy space shuttle to show for our last 30 years of human progression!

Before we can build great power stations in the sky, we must first stop taking free rides off the backs of the space heroes of the Kennedy administration, and rebuild our space program into what it was over three decades ago!

Daniel M. Ikeda

And getting back to the subject of alien intelligence, a reader in New Zealand provides this perspective:

To the Editor:

It is interesting that the debate about extraterrestrial intelligent life and aliens now seems to have gone the way of worn out Hollywood icons, or excommunicated members of the British royal family. It is a pity you now need someone of importance to create a newspaper headline that could attract attention to bring out the true facts.

Other alien life-forms and extraterrestrial intelligence do participate in the inhabitancy of this planet we call Earth as they have done for many generations. Many years ago as a child I had several encounters with these other life forms. These experiences taught me much. Not only of a multitude of extraordinary insights into the future of the human race, but also how many people in the present were prepared to profit from my experiences. U.S. Military defense learnt much in technology from them, some of which is still hidden in classified secrets. Others would trivialize or joke, write books or make movies about my experiences and publish personal photos without formally recognizing or compensating for their use. I despair when I see so many prepared to play games of self-interest while failing to see the real picture of what life is all about. Perhaps I should ask, is it because they are afraid of the truth that we are not an unique life form on this planet or in this universe?

We look further into space, and also find similar things when we look inside ourselves. Another mystery that we all need to cling to. As we solve one, we look for another. This is scientific exploration. I enjoy it, just as much as part of my religion and philosophy, which is just to sit back and enjoy the mystery without always worrying about finding the solutions to the puzzles placed before us.

What many of the world's population (as it expands) have yet to learn that does not come from these outside (alien) influences, is how we can live together and survive, as Earth's resources slowly dwindle under humankind's mismanagement of the planet's ecological resources.

Unless our space exploration can also be directed at the complete understanding of our own planet, we and our fellow beings will end up ultimately like the dinosaurs. Past inhabitants, and littering the land as piles of bones and dust amongst all the other rubbish we accumulate in our consecutive lifetimes.

Scientific knowledge is a major part of our future -- let us make sure everything is done right, and in a proper perspective if we are to have a future.

Frank R May, New Zealand