NASA/JPL/Cornell University

NASA's Opportunity rover, the third robotic wanderer to land on Mars, changed our understanding of the Martian landscape, geology, atmosphere and history. On Wednesday, NASA announced its mission complete and with it, the rover's life officially over. The plucky robot roamed the Martian surface for approximately 5,515 Earth days, just over 15 years.

During a press conference, NASA said that Opportunity hadn't responded to a last-ditch effort Tuesday to establish contact. A planet-encircling dust storm cut off communications with Opportunity on June 10, 2018, preventing its solar panels from storing power. Since then, over 830 rescue commands had been beamed to the rover.

On Tuesday night, despite the transmission of commands and Billie Holiday's I'll Be Seeing You to Mars via the Deep Space Network, the rover couldn't be roused.

"I learned this morning that we had not heard back," Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate, said during a press conference.

"It is therefore that I am standing here with a sense of deep appreciation and gratitude [and] I declare the Opportunity mission as complete," he concluded.

NASA Administrator Jim Bridenstine shared his thoughts on Twitter, as did many emotional space fans.

After 800+ attempts to contact @MarsRovers Opportunity, today we’re announcing the end of a successful Martian mission. Intended to explore the Red Planet for 90 days, Oppy outlived its mission lifetime by 14+ years. Join us live now: https://t.co/zJwTTpQNwp #ThanksOppy pic.twitter.com/U4J26TfzDv — Jim Bridenstine (@JimBridenstine) February 13, 2019

Opportunity's story is one of resilience, discovery and wonder. It's a record-breaker, a testament to the prowess of the engineers, scientists and leaders at NASA who built, worked on and piloted the rover for over 14 years. Its final resting spot lies on the western edge of the Endeavour crater, in a gully the science team dubbed Perseverance Valley.

Now playing: Watch this: 'Overachieving' Mars rover Opportunity mission over after...

The rover launched on July 7, 2003, and landed in Meridiani Planum on Mars on Jan. 25, 2004. Its original mission was intended to last just over three months, but the hardy rover continued to roam across the Martian soil for nearly 15 years, traveling 28.06 miles (around 45 kilometers) -- the farthest distance achieved by any extra-planetary robot.

It was the second of twin rovers sent to the planet in 2003 as part of the Mars Exploration Rover (MER) mission. The first rover, Spirit, became stuck in a sand trap in 2009. NASA officially announced its mission complete in 2011.

Opportunity made several landmark discoveries on Mars, chancing upon the first meteorite found on another planet, revealing that Meridiani Planum was once immersed in water, studying over 100 impact craters and delivering countless stunning panoramas of a planet nearly 34 million miles away.

After landing in 2004, the golf-cart-sized robot began its journey to Endurance crater, spending six months performing an extensive investigation of the bedrock and sand dunes. Opportunity would move on to study the roughly half-mile-wide (730 meters) Victoria crater between 2006 and 2008, revealing how water had entered and left the region billions of years ago.

In 2011, it reached Endeavour, an impact crater 13.7 miles wide, after three years of travel. It discovered a bright mineral vein of gypsum. At the time, Steve Squyres, a principal investigator on the mission, said, "This tells a slam-dunk story that water flowed through underground fractures in the rock." It also snapped an image of the infamous "dust devils," whirlwinds that occasionally arise on the Martian surface.

Its journey was not without some scares. In 2005, Opportunity got mired in a dune -- a fate that had crippled and eventually claimed its robotic twin. On Earth, NASA worked to mimic the Martian soil before executing careful maneuvers to free Opportunity. The rover weathered its first dust storm in 2007, wrestled with intermittent wheel problems and labored with a problematic robotic arm throughout its expedition.

NASA/JPL-Caltech

Still, it seemed that nothing could knock out the intrepid robotic explorer. On its 5,000th Martian day, it celebrated with its first selfie.

Opportunity will remain dormant in Perseverance Valley, occasionally being spied by a passing orbiter -- or perhaps, in the distant future, retrieved and idolized as a pioneer that pointed the way for the first humans to reach, and even settle on, Mars.

"It is because of trailblazing missions such as Opportunity that there will come a day when our brave astronauts walk on the surface of Mars," Bridenstine said.

The robot is survived by NASA's Curiosity rover, which remains the only active rover on the Martian surface. It will be joined by NASA's planned Mars 2020 rover and Rosalind Franklin, the European Space Agency's rover, set to launch in 2020.

NASA turns 60: The space agency has taken humanity farther than anyone else, and it has plans to go further.

Taking It to Extremes: Mix insane situations -- erupting volcanoes, nuclear meltdowns, 30-foot waves -- with everyday tech. Here's what happens.