A new island born from an explosive submarine volcanic event in early 2015 may help NASA scientists answer a few questions about similar processes on other planets.
The island, located in the southwestern Pacific Ocean in the Kingdom of Tonga, is unofficially named Hunga Tonga Hunga Ha’apai (HTHH); a mouthful designation in honor of the two older islands it rose between. While HTHH's rapid formation, rising over 500 feet above the water and spanning 1.1 miles in a little over a month, was chronicled in great detail using satellite imagery, NASA researchers were eager to preform on-the-ground observations.
"Volcanic islands are some of the simplest landforms to make," Jim Garvin, chief scientist of NASA's Goddard Space Flight Center, said in a statement. "Our interest is to calculate how much the 3D landscape changes over time, particularly its volume, which has only been measured a few times at other such islands. It's the first step to understand erosion rates and processes and to decipher why it has persisted longer than most people expected."
The original expectation was that HTHH would be reclaimed by the sea almost as quickly as it was formed. While island formation on Earth is an ongoing process, it's rare for them to last long due to quick erosion by both the sea and rainfall. In fact, over the last 150 years, NASA says HTTH is only the third eruption to have lasted over a few months.
In October, NASA researchers had the opportunity to join the few humans ever to set foot on this new land.
"We were all like giddy school children," research scientist Dan Slayback said of their visit. "Most of it is this black gravel, I won't call it sand — pea sized gravel — and we're mostly wearing sandals so it's pretty painful because it gets under your foot. Immediately I kind of noticed it wasn't quite as flat as it seems from satellite. It's pretty flat, but there's still some gradients and the gravels have formed some cool patterns from the wave action."
In addition to being surprised by the vegetation already taking root on the new landmass, Slayback says the team also experienced an odd "sticky" mud emanating from the island's volcanic cone.
"In the satellite images, you see this light-colored material," he said. "It's mud, this light-colored clay mud. It's very sticky. So even though we'd seen it we didn't really know what it was, and I'm still a little baffled of where it's coming from. Because it's not ash."
In addition to measuring the island's elevation, the research team also collected rocks to figure out how HTTH has managed to persist for so long. As shown in the time lapse of 33 months of satellite imagery below, however, erosion is slowly taking its toll.
"The island is eroding by rainfall much more quickly than I'd imagined," added Slayback. "We were focused on the erosion on the south coast where the waves are crashing down, which is going on. It's just that the whole island is going down, too. It's another aspect that's made very clear when you're standing in front of these huge erosion gullies. Okay, this wasn't here three years ago, and now it's two meters (6.5 ft) deep."
The NASA researchers are particularly intrigued with how the island's erosion can provide insights into more otherworldly mysteries, like Mars' once-wet past.
"Everything we learn about what we see on Mars is based on the experience of interpreting Earth phenomena," Garvin said. "We think there were eruptions on Mars at a time when there were areas of persistent surface water. We may be able to use this new Tongan island and its evolution as a way of testing whether any of those represented an oceanic environment or ephemeral lake environment."
At the present rate of erosion, researchers believe the island could keep itself above the waterline for at least another decade. In the meantime, Slayback and his team will continue making visits to understand more about the island's formation and what processes might be underway to help it survive where other virgin landmasses have perished.
"It really surprised me how valuable it was to be there in person for some of this," he said. "It just really makes it obvious to you what is going on with the landscape."