Letters from the July 30, 2005, issue of Science News

Led astray

The illustration of the solar system in “Roaming Giants: Did migrating planets shape the solar system?” (SN: 5/28/05, p. 340) does not represent the current orbit of the planets. Rather, it must be a frame from the computer simulation referred to in the article.

William Meadows
Dripping Springs, Texas

Indeed, the image reflects the computer-simulated planet orbits of the early solar system, not as the caption states, current orbits.—R. Cowen

Of one mind

There is information that when we imagine things, we activate some of the same brain mechanisms as when we experience them physically (“Mapping Aroma: Smells light up distinct brain parts,” SN: 5/28/05, p. 340). It would be interesting to know whether imagining the scent of a food that one likes “lights up the brain” as actually smelling that food does. Seems like a reasonable description of what I personally experience.

Bal Simon
Bellevue, Wash.

According to Zhihua Zou of the Fred Hutchinson Cancer Research Center in Seattle, neuroimaging studies of people recalling odor, taste, visual, and auditory imagery reveal that these processes activate brain areas that are largely overlapping with, “but not identical to,” those activated by actual sensory stimuli. The more details in the imagery, the more similarity in brain activity there is between imagery and perception, studies have found.—C. Brownlee

Red and cloudy

Your stories on a time when Mars was wet (“Roving on the Red Planet,” SN: 5/28/05, p. 344) should also point out that only a very thick atmosphere could have allowed the surface temperature to be high while the radiation output from the sun was only 70 percent that at the present.

J. Thomas Baylor
Austin, Texas

Theorists agree that the atmosphere of Mars was thicker when the planet was wetter. They’re less certain that the sun was 30 percent weaker then.—R. Cowen