Dr. Sylvia Earle explores Australia's Great Barrier Reef in a scene from 'Mission Blue' (© Bryce Groark/AP Photo/Netflix)

'Mapping Courage: Honoring W.E.B. Du Bois & Engine #11,' a mural by Willis Humphrey, Philadelphia, PA (© Christian Carollo/Shutterstock)

Meerkat family huddling together (© stefbennett/Shutterstock)

Moai statues at Ahu Tongariki in Rapa Nui National Park, Easter Island, Chile (© blickwinkel/Alamy)

Sigiriya Rock, Central Province, Sri Lanka (© Jeremy Woodhouse/Getty Images)

Bubbles in the ice of Abraham Lake in Alberta, Canada (© robertharding/Alamy)

A snowdrop in bloom (© Péter Hegedűs/Getty Images)

View of the Old City in Quebec City, Canada (© RENAULT Philippe/age fotostock)

Lantern Festival in Pingxi, Taiwan (© Jung-Pang Wu/Getty Images)

The Hollywood Sign overlooking Los Angeles, California (© Sean Pavone/Shutterstock)

Aerial view of Superkilen, a park in Copenhagen, Denmark (© Oliver Förstner/Alamy)

Pinzon Island tortoise hatchling emerging from its egg at the Charles Darwin Research Station on Santa Cruz Island, Galápagos Islands, Ecuador (© Pete Oxford/Minden Pictures)

Frozen amphitheater of columnar basalt walls flanking Abiqua Falls, Oregon (© Joshua Meador/Tandem Stills + Motion)

A heart-shaped hole in the rock formation of Calanques de Piana in Corsica, France (© joningall/Getty Images)

The 2019 Lemon Festival in Menton, France (© Mandoga Media/Alamy)

The 2019 Lemon Festival in Menton, France (© Mandoga Media/Alamy)

Zwergplanet Pluto aufgenommen von der NASA-Raumsonde New Horizons (© NASA/JHUAPL/SWRI/Science Photo Library)

Pluto's crescent imaged by NASA's New Horizons interplanetary space probe (© NASA/JHUAPL/SWRI/Science Photo Library)

Wandering albatross pair, South Georgia Island (© David Tipling Photo Library/Alamy)

Rifugio Lagazuoi above the clouds with Monte Pelmo in the background, Dolomites, Italy (© Nicolo Miana/eStock Photo)

Giant puppets for Carnival in Olinda, Brazil (© Pulsar Imagens/Alamy)

The interior of the Great Temple of Ramesses II, Abu Simbel, Egypt (© Nick Brundle Photography/Getty Images)

People ice fishing on Gull Lake in Brainerd, Minnesota (© Robert Benson/Cavan)

Pilgrims throwing wind horses into the air above Ganden Monastery for the New Year in Tibet, China (© Ian Cumming/plainpicture)

The Roots of Music Cultural Sculpture Garden in Louis Armstrong Park, New Orleans, LA (© jejim120/Alamy)

Acadia National Park in Maine (© emptyclouds/Getty Images)

A polar bear sow and her cubs in Alaska's Arctic National Wildlife Refuge (© Steven Kazlowski/Minden Pictures)

Otter Creek in winter, Brandon, Vermont (© Caleb Kenna/Offset)

Scenic deep tropical forest of Janjehli, Himalayas (© KS-Art/iStock/Getty Images Plus)