Lots of things may stop Earthlings in general and NASA astronauts in particular from ever exploring Mars. Cost is a real issue. So, too, are hurdles like building a safe, reliable vehicle to get there or the risk of being cataclysmically struck by errant space debris.

Add to the list this problem: Cosmic radiation.

A government panel reviewing NASA's planned and proposed human space flight activities says sending astronauts to one of Mar's moons, such as Phobos (pictured) or Deimos, is possible, but only if the radiation threat can be solved.

So far, it has not. Cosmic radiation consists of speeding protons and heavier atomic nuclei zipping through the solar system constantly, in all directions. Passing through living cells, it can slice up DNA, resulting in eventual cancer.

Humans on Earth are protected by the planet's atmosphere and magnetic field, which also provides partial protection to astronauts on the International Space Station. Still, space missions are kept short enough to reduce radiation risks.

Venturing out beyond the moon, however, exposes space travelers on long trips to extended, unabated radiation. Effective shields are too thick and heavy to be practical. Alternative technologies like plasma bubbles are still just drawing board notions.

Until an answer is found, all talk of astronauts safely visiting Mars is wildly speculative. They might actually get there and back, but they'd be at high risk of bringing back a nasty case of cancer, too.

VERBATIM

Unless citizens themselves become inconvenient, the truth will remain a minor consideration.

— Author-activist Mark Engler on how civil disobedience may be necessary to combat global warming

BRAIN SWEAT

The same five letters can be rearranged into two different words to fill in the blanks in the following statement: The Neanderthal shook a primitive sort of ——-. It was too heavy to use against some of the faster animals, but it seemed to work against ——-.

'TRUE FACTS'

Houseflies hum in the key of F.

BRAIN SWEAT ANSWER

SABER (or SABRE) and BEARS

JUST ASKING

If a tree falls in the forest, do the other trees laugh?

QUIRKS OF NATURE

Glyptodonts were ancient armored mammals that sported hefty tails they could use for defense. New research suggests that, like modern baseball players, they tried to hit a sweet spot by landing powerful blows with the tip of their tails, so that potentially harmful vibrations were minimized.

SURELY YOU'RE JOKING

Scientific, medical and academic papers are often rife with jargon. Here's an abridged (and completely unscientific) guide to some of the more common phrases used:

It has long been known — I didn't look up the original reference

In my experience — Once

In case after case — Twice

In a series of cases — Three times

It is believed — I think

It is generally believed — A couple of others think so, too

Typical results are shown — This is the prettiest graph

Correct within an order of magnitude — Wrong

WHAT IS IT ANSWER

A life-sized, bronze Roman horse's head, the first ever found in Germany and one of the best-preserved Roman bronzes yet uncovered.

The sculpture, part of a statue believed to be of the Roman emperor Augustus, was discovered at Waldgirmes, which was once a Roman outpost in what is now Bavaria. The horse's head was unearthed while excavating a 33-foot-deep wood-reinforced well shaft. The head is roughly 2,000 years old.

To find out more about Scott LaFee and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.