Mary Batten’s latest book, “Life in Hot Water:Wildlife at the Bottom of the Ocean,” plunges more than a mile below the surface of the sea to the most extreme environment on the planet — hydrothermal vents. 

“This is a world without sun, where water hot enough to melt lead gushes from bizarre chimneys,” she says, adding, “Discovery of the vents is one of the greatest scientific adventures of the 20th century.” Batten’s book, stunningly illustrated by Thomas Gonzalez, details that adventure in a fast-paced narrative loaded with facts that have the flavor of science fiction.

For years geologists had predicted the existence of hydrothermal vents in the deep ocean, but there was no evidence to support their prediction. Then an expedition using towed temperature-measuring instruments identified an area of the mid-ocean ridge near the Galápagos Islands as a likely place to find vents. The Alvin, a deep-diving human-occupied vehicle (HOV) operated by Woods Hole Oceanographic Institution in Falmouth, Massachusetts, made a visit possible. On Feb. 17, 1977, a pilot and two scientists got the ride of their lives. They expected to find a barren landscape, but what they saw was beyond anything they imagined.

Jets of hot, dark-colored fluids were exploding upward like geysers from a section of the mid-ocean ridge, the longest mountain range on Earth. You can’t see it because it’s at the bottom of the sea where it snakes more than 40,000 miles around the planet.

“Unbelievably, creatures never seen before were living around the vents,” Batten says. Strange tube worms, mussels, giant clams, crabs, blind shrimp — an entire ecosystem was thriving in conditions where no life was thought possible. Because these animals can tolerate such extreme conditions, scientists call them “extremophiles.” 

Batten explains that until vents were discovered, scientists thought green plants and sunlight were the basis of all food chains through the process called photosynthesis. But no green plants grow on the ocean floor and sunlight never penetrates these depths. 

So what were they eating? In what American oceanographer Robert Ballard, who discovered where the sunken Titanic lay, called “probably one of the biggest biological discoveries ever made on Earth,” scientists discovered that vent creatures feed on bacteria that eat the toxic chemicals in vent fluid. Scientists called the process chemosynthesis. Textbooks had to be rewritten to include two kinds of food production: chemosynthesis powered by energy from the Earth and photosynthesis powered by the sun.

In an Author’s Note, Batten says some scientists theorize that chemosynthesis may have powered the evolution of life beyond Earth, possibly below the surface of Mars and on Jupiter’s moon Europa. Although marketed for children, this book is full of information that will fascinate adults. For more information, see the author’s website: marybatten.com