cold fjord notes that the X Prize Foundation has opened up a new mission: to quantify the acidification of the world's oceans, excerpting from a description on Nature's blog of the project's focus: "Scientists who study ocean acidification must confront a fundamental problem: It is hard to measure exactly how much the ocean's pH is changing. Today's sensors don't work well at depth or over long periods of time, and they are too expensive to deploy widely. That is where the US$2 million Wendy Schmidt Ocean Health X Prize comes in. The 22-month competition will award two $1 million prizes, one to the best low-cost sensor and one to the most accurate. The competition's organizers decided to award two prizes because the two goals present different engineering challenges. ... As carbon dioxide levels rise in the atmosphere, ocean water takes up some of the gas and becomes more acidic. This can harm shell-building marine life like coral, whose calcium carbonate skeletons dissolve in the increasingly acidic water. All of this research is bedeviled by the simple lack of technology to monitor ocean pH in real time across the world."