The Swiss team tests a laser mapping submersible in Lake Annecy in France.

XPRIZE

Apenas 18% do fundo do oceano foi mapeado. XPRIZE drones poderia mudar isso

By Julia RosenOct. 31, 2018 , 10:50 AM

Na próxima semana, um pequeno barco de listras amarelas e brancas sairá do porto em Kalamata, na Grécia, e partirá da costa. O navio não carrega um capitão ou tripulação, apenas uma série de componentes eletrônicos que lhe dirá para onde ir e quando soltar a cápsula em formato de torpedo que está na popa. Uma vez liberado, o veículo equipado com sonar descerá vários quilômetros até o abismo gelado da Trincheira Helênica, a parte mais profunda do Mar Mediterrâneo, e mapeará o fundo do mar com pulsos de som. A equipe por trás do esforço é a primeira das oito competidoras nos próximos meses na final do US $ 7 milhões do Shell Ocean Discovery XPRIZE. "Não tenho certeza se estamos loucos ou não, mas decidimos ir primeiro", diz Rochelle Wigley, geóloga marinha da Universidade de New Hampshire, em Durham, que lidera a equipe XPRIZE da Fundação Nippon japonesa e do General Carta batimétrica dos oceanos (GEBCO), uma organização internacional.

A XPRIZE, uma organização sem fins lucrativos com sede em Culver City, Califórnia, realiza competições para estimular a inovação e, em 2015, voltou-se para o problema de mapear o fundo do oceano, diz a diretora do concurso, Jyotika Virmani. O catalisador foi o desaparecimento do Vôo 370 da Malaysia Airlines em algum lugar sobre o Oceano Índico, e a completa percepção de que as equipes de recuperação sabiam pouco sobre o que estava abaixo da superfície da área de busca. "Em vez do avião, infelizmente, eles encontraram dois novos vulcões, um dos quais é maior que o Vesúvio", diz ela.

Sharper pictures of the ocean floor could help companies look for resources such as oil. (The energy company Shell is the prize’s sponsor.) But researchers want a clearer view, too. For example, Dave Clague, a geologist at the Monterey Bay Aquarium Research Institute in Moss Landing, California, studies volcanic activity along midocean ridges—submarine mountain chains that generate new ocean crust—by identifying lava flows. But scientists have fine-scale maps for only a tiny fraction of the 65,000-kilometer-long system, limiting their understanding of how new crust forms and what happens to it as it moves away from the ridge.

Biologists also need better maps, to manage fisheries and identify deep-sea habitats. They have already discovered new colonies of cold-water corals just by looking for structures rising from the sea floor, says Craig Brown, a mapping expert at Nova Scotia Community College in Halifax, Canada. “They usually have quite dramatic topography,” he says.

So far, just 9% of the seafloor has been mapped in detail with modern sonar technology, Wigley says, and only 18% of the world’s ocean bottom has been surveyed at all, often at resolution so coarse that jumbo jets—and volcanoes—would have no trouble hiding. The rest—four-fifths of the two-thirds of the planet covered by water—is virtually unknown. As usual, the limitations are money and time. The research vessels that do high-resolution mapping cost up to $100,000 a day to operate. And they move so slowly that it would take centuries for them to chart the world’s oceans, Virmani says.

Corrida para o fundo

The eight teams competing for the ocean mapping XPRIZE use a mix of uncrewed surface vehicles and autonomous underwater vehicles (AUVs).

Team Name	Country	Surface Ops	Number of AUVs
Arggonauts	Germany	Five ships	Five
Blue Devil Ocean Engineering	United States	Two aerial drones	Two
CFIS	Switzerland	None	20
GEBCO-Nippon Foundation alumni	International	One ship	One
Kuroshio	Japan	One ship	Two
PISCES	Portugal	One ship, two acoustic beacons	One
Team Tao	United Kingdom	One ship	Five
Texas A&M	United States	One ship	One

(DATA) XPRIZE teams

Os satélites também podem mapear o fundo do mar, medindo pequenas variações na superfície oceânica causadas pela atração gravitacional de características maciças do fundo do mar. Mas a resolução é grosseira. Nos últimos anos, os pesquisadores se voltaram para veículos subaquáticos autônomos (AUVs). Eles seguem caminhos pré-programados usando sistemas de navegação inercial que rastreiam precisamente sua velocidade e direção, e transportam sonares de vários feixes em miniatura. Ao cruzar perto do fundo do oceano, eles podem detectar contornos no fundo do mar menores que um metro - uma grande melhora em relação à resolução de 50 metros de um sistema típico baseado em navios que trabalha no fundo do oceano, diz Clague, que não está envolvido. o concurso XPRIZE. Mas os AUVs ainda são lentos. Esforços para adicionar baterias e aumentar o tempo de mergulho apenas aumentam o AUV, exigindo navios maiores para lançá-los, “o que acaba com o objetivo”, diz Clague.

XPRIZE hopes its competition will spark faster, cheaper autonomous systems. Starting from shore, the eight finalists must map between 250 and 500 square kilometers in 24 hours, at depths down to 4000 meters and resolutions of 5 meters or better. They must also carry instruments to collect images of 10 interesting features and find a trophy stashed on the sea floor. The technical challenges include building instruments to withstand enormous pressure, balancing battery life against speed, and making the robots smart enough to carry out the whole operation without human guidance. “Everything is hard,” says Martin Brooke, an engineer at Duke University in Durham, North Carolina, and leader of its XPRIZE team.

Brooke’s group—mostly engineering students—will try to gain time by using heavy-lift aerial drones to carry buoys that will lower tethered mapping pods into the ocean. Most teams use an autonomous surface vessel to save their AUV’s precious power and to serve as a communication hub. The Swiss CFIS team, led by Toby Jackson, a financial trader–turned–inventor, will send 20 lightweight, 3D-printed AUVs directly from shore. Instead of sonar, they will use lasers, which can bounce light off the sea floor because they are at such close range.

Team Tao will also use a swarm approach, launching five custom-built AUVs from an autonomous catamaran it calls the “vending machine.” Eventually, the system will carry two dozen subsea drones, says team leader Hua Khee Chan, an engineer at Newcastle University in the United Kingdom, allowing half to work while the others charge. Each AUV will follow a simple vertical path, enabling it to sample the temperature and salinity of the water column as it descends. Chan says it’s “extra data that we get for free while it’s traveling.” Both Chan and Jackson say they aim to produce their AUVs for less than $25,000 a pop—a bargain compared with the sophisticated models used today, which can cost $1 million or more.

Cheaper, more flexible systems could help researchers rapidly fill the gaps in seafloor maps—and enable repeat surveys to monitor changes over time. Clague would like to measure how much lava is produced during a single eruption on a midocean ridge, which gives clues about magma generation in the mantle. Repeat mapping could also track movement along offshore faults that generate earthquakes, and in seafloor sediments after major weather events.

As XPRIZE’s sponsor, Shell reserves first rights to negotiate with each team for use of its technology, which it could use for oil and gas exploration or to monitor production wells and pipelines. Companies hoping to mine the seafloor for minerals are also eager to get a better look. But Wigley says mapping could also aid in marine protection. “If we understand the seafloor better, we can manage where it’s happening better and understand the impacts better.”

For now, that’s a long way off, and most teams are just scrambling to prepare for the competition in Greece. A Portuguese team still hasn’t tested its acoustic positioning system, which relies on a constellation of floating beacons, in deep water. “From the math, it should work,” says team leader Nuno Cruz, an engineer at the University of Porto in Portugal. “But you go into the ocean and things are not like math.” Some teams already know they won’t win, but they are fine with that. Most entered for the challenge, not the purse, and XPRIZE is pleased with the progress they’ve made, Virmani says. “We’ve already shifted the field.”

*Correction, 31 October, 4 p.m.: An earlier version of the story misstated the resolution and coverage rate of typical AUVs.

Posted in:

• Oceanography

doi:10.1126/science.aav9034