Ways of searching for life on Mars are ten a penny, but here’s the latest suggestion, based on studies performed on rocks in Earth deserts. These rocks are covered with ‘desert varnish’, a patina of silica and other elements deposited on the rocks over time by wind and weather, trapping fragments of organic DNA as the layers are laid down. If we can find Martian rocks with a similar coating, a vigorous scraping of samples could yield evidence of life in the Red Planet’s past.