Permafrost, ground frozen year-round, covers vast areas of the Arctic and sub-Arctic, and as it thaws it releases greenhouse gases and damages roads and buildings. Because it lies underground, mapping it over wide areas is hard. A new approach flies an electromagnetic instrument over the land: frozen ground resists electric current far more than thawed ground, so measured resistivity reveals where permafrost is and how thick it is. Surveyed over Canada's Mackenzie Valley, it showed that thawed zones called taliks often sit beneath lakes and rivers and link up, letting water flow between them; one under the Mackenzie River was 2 km wide and over 75 m deep. Land burned by wildfire decades ago still has warmer permafrost near the surface.

Indonesian Vice President Gibran Rakabuming Raka handed his resignation to parliament after questions were raised about his eligibility for office and his academic credentials. Gibran is the son of former president Joko Widodo, and his resignation came as Widodo publicly backed the president, Prabowo Subianto. Gibran had been elected vice president in 2024 as Prabowo's running mate. His candidacy was made possible by a 2023 Constitutional Court ruling on the minimum age for candidates, which was itself controversial. Parliament will now consider the resignation.

Angkor, near Siem Reap in northern Cambodia, was the capital of the Khmer Empire, which ruled much of mainland Southeast Asia between roughly the 9th and 15th centuries. At its height the city spread across about 3,000 square kilometres, making it the largest pre-industrial city on Earth by area. Its growth depended on water: huge reservoirs called barays, along with canals and embankments, stored monsoon rain and carried it to rice fields. That system let farmers harvest more than once a year and fed a very large population through the dry season. The temple complex of Angkor Wat, built in the early 12th century, is the best-known monument and still stands at the heart of the park.