Earth’s newest island has clues to Mars’ past

Geological similarities could help shed light on ancient Martian history.

The planet’s youngest island was not expected to survive more than a few months. Its survival makes it a geological treasure trove that may hold clues to questions about ancient Mars.

Hunga Tonga Hunga Ha’apai, in the archipelago ßof Tonga, rose out of the South Pacific ocean in a month-long volcanic eruption from December 2014 to January 2015 – so fast you could watch it grow.

A cone of loosely consolidated volcanic ash formed the island, which scientists expected the South Pacific surf to pound back in months. But it persists, standing 120 metres tall at its highest point and measuring about two kilometres across, scientists reported at a meeting of the American Geophysical Union in New Orleans in December.

They now think Hunga Tonga Hunga Ha’apai could last anywhere between six and 30 years. One reason for this longevity is the eroded material piling up in the shallow waters that has connected it to two neighbouring islands and formed a more stable barrier.

“That’s allowing the system to partially survive,” says Jim Gavin, of NASA’S Goddard Space Flight Centre.

The chance to study the island’s evolution not only helps better understand the history of Earth but also of Mars, which has thousands of geological features with similar size and shape.

Many scientists think those features might be due to volcanic eruptions beneath shallow seas about one to two billion years ago. What were once Martian islands were left as low isolated peaks when oceans dried up.

Studying Hunga Tonga Hunga Ha’apai might help determine the depth of the water in which these Martian islands sat and how long that water persisted. Not that the parallel is perfect; whatever oceans existed on Mars were nowhere near as big as the Pacific Ocean. So the processes affecting the Martian islands would be much slower than those affecting the new Tongan island.

Nonetheless, Gavin says, Hunga Tonga Hunga Ha’apai “will give us windows onto the times on Mars when we think there were standing bodies of water” – one of the “holy grails” of Martian ancient history.