Our Second Home World?

As a kid, I wanted to go to Mars. I played a game called “Going to Mars” with my sibs and cousins, and it was the most exotic place we could think of. Later on, in college, I wanted to be part of a Mars team, but ended up studying comets (that’s what happens when your advisor’s grant money is focused on comet studies). I always kept my love of Mars going, and figured someday I’d get to go. Of course, that was back when it looked like a crewed Mars mission would be happening by the end of the 20th century or maybe 2015 at the latest.

Today, the human mission to Mars possibilities are kind of limited. One: you can go with your spouse on a three-year flyby (and never land), or two, you can join with a crew that will land and probably  not come back.

Okay, both of them kind of appeal to the pioneer spirit in many of us, but gosh, by now I’d thought we’d have more chances and choices.  One mission scenario I remember from my days in the academic world was to build bases on the Moon, use those or orbital stations to build trans-Mars ships while training crews for eventual missions to the Red Planet. Once there, crews would set up a rotating visit schedule so that while some crews were on the ground doing survey work, others would be in orbit and/or heading back to Earth so that the next round of Mars visitors could make their way out.

Will those plans ever happen?  Hard to tell. I think that such exploratory missions will progress much as the exploration of Earth did: sending small groups out to do the survey work, and then when things looked safe (or as safe as they could be), the families and governments and companies followed along. Of course, we see how well that worked in some parts of the world, so maybe the future Mars explorers will find a way to do it better that we did here.  Not that Earth is a training world; right now it’s the only place we have, and we’re kind of not treating it too well. That, too, will change, when the realities of climate change grow more apparent to more people.  These are one-of-a-kind planets we have here, and Earth IS our home world. Mars, because of its very different weather conditions, atmospheric pressure, gravity, and other factors, will not be humanity’s assured second home.  It will be a place where we send our children, and then THEIR children will make it their home. How long before humanity adapts to Mars?  Good question.

All Your Light Are Belong to Us

Here’s an interesting thing to ponder as you’re out watching the reflected light from the planets gleam at you over the next few nights:  almost all the photos of light (and this includes everything from ultraviolet to far infrared) ever emitted by all the galaxies that ever existed in the history of the universe is still traveling through the universe.

Light contains information about the universe in all its phases throughout history. If we could carefully measure the number and energy (the wavelength) of all the photons of light throughout history, we’d know some pretty cosmic things. In a very cosmic sense. We might find out how galaxies of long ago differed from those of today, for example.  This “extragalactic background light” is tremendously difficult to measure, though. We’re inside a very bright galaxy, and that drowns out this bath of ancient and young photons.  So, astronomers are looking for other ways to measure this bath of light from across time and space.  They found one, by measuring this background light by looking at the absorption of very high-energy gamma rays from distant blazars. Those are supermassive black holes in the centers of galaxies that are pointing their jets right at us across space.  Not all the gamma rays reach us — so scientists figured out how much gamma radiation is missing by studying the gamma rays that DO reach us.

This technique yielded a HUGE result. Astronomers have been able for the first time to measure the evolution (changes in) the extragalactic background light over the past five billion years — essentially since about the time the Sun and planets began to form. And, they found out that the kinds of galaxies we observe today are responsible for all the EBL over all time. There are more distant, earlier galaxies emitting gamma rays, but they are beyond what’s called the Cosmic Gamma Ray Horizon, and that poses more challenges to astronomers wanting to measure light from even earlier times.

Still, it’s an interesting way to study the universe. And, on a late spring night, when you’re out looking at the planets in the west after sunset, it’s interesting to ponder what else there lies out there to be discovered.

Want to know more about this study?  Check out the University of California’s High-Performance Astrocomputer Center’s announcement about this discovery.