Our first forays into the solar system have revealed little in the way of lush and verdant landscapes. But there is a lot of H2O out there — it’s just not very wet. In “Tour Our Wet Solar System,” writer Michael Carroll ticks off the likeliest extraplanetary watering holes. Mercury, the closest planet to the sun, still has some ice socked away at its poles in deep craters where sunlight never reaches. Mars started out relatively wet, but due to its low gravity, it lost most of its water. Some of it remains frozen at the planet’s poles and also, scientists suspect, underground. But most of our solar system’s water lies farther out. Beneath its icy crust, for example, Jupiter’s moon Europa is thought to have an ocean that’s 60 miles deep. And there’s even more water flitting through space, frozen into asteroids, comets and Saturn’s rings, which contain water-ice in amounts that would dwarf Earth’s oceans.
In his book, physicist Neil Downie provides a series of do-it-yourself science experiments that stand apart from your ho-hum Mr. Wizard-fare because, well, they involve a few high-speed projectiles. First up: A handy how-to guide for building a pressure cannon that can launch BBs made from carrots. The device is definitely not just an excuse to blast vegetable matter across the back yard: It also illustrates Boyle’s law, which describes the relationship between pressure and volume of gas. Downie has some experiments that are more benign — using mints to turn a bottle of diet soda into a gusher, and exploding balloons by using sunlight and a magnifying glass — but many others involve some sort of “boom.” And Downie is clear about safety requirements and risks. “This is NOT a book about doing dangerous demonstrations because they are dangerous,” he writes in the book’s introduction. “Rather, it is about doing interesting projects, some of which happen to have elements of danger.” All you need are a few household items, some good judgment and, possibly, a carrotproof vest.