A dust storm that enveloped Mars for nearly 100 days is finally clearing up.

NASA's Opportunity rover slept through the storm to keep its batteries charged, but the robot has yet to wake up and contact NASA.

Opportunity will fail if it can't power heaters that protect the robot from frigid, circuit-snapping temperatures on Mars.

A satellite orbiting Mars took a photo of the rover, which — along with 3D illustrations — shows the exact hill where Opportunity is located.

NASA may give up trying to contact the rover on a daily basis after October, perhaps signaling the 15-year mission's end.

A satellite orbiting Mars has taken a remarkable yet potentially somber photo of NASA's longest-lived robot on the red planet.

That robot is the Mars Opportunity rover, which is about the size of a golf cart, landed in January 2004, and was supposed to last 90 days. However, Opportunity has explored Mars for more than 15 years and trekked more than 28 miles across the planet using solar energy.

Its days may be numbered, though.

When a global dust storm began to envelope Mars about 100 days ago, Opportunity stopped getting enough sunlight to its solar panels. This triggered it to go to sleep on June 10 and conserve battery power, which the rover needs to run heaters that protect its circuits from blistering Martian cold.

"The rover's team at NASA's Jet Propulsion Laboratory in Pasadena, California, hasn't heard from the rover since," Andrew Good, a representative for the lab, wrote in a press release.

Though a new satellite image gives mission controllers hope that Opportunity will wake up, the mission may be nearing its end.

What a new satellite image of Opportunity shows

A satellite image of NASA's Opportunity rover on Mars after a global dust storm finally cleared. NASA/JPL-Caltech/Univ. of Arizona; Business Insider

Opportunity was descending into a location called Perseverance Valley when the storm hit in early June. This blocked satellite views of the ground there.

Since dust levels have plummeted in the past couple of weeks, though, NASA was able to clearly photograph Opportunity's location on September 20 using the Mars Reconnaissance Orbiter (MRO).

That satellite image, shown above, was taken by an MRO instrument called HiRISE. In the picture, there is an unmistakable though almost indiscernible ruddy bright spot on the slopes of a hill: the Opportunity rover.

A before-and-after image created by NASA's Jet Propulsion Laboratory at Caltech more clearly shows where the rover stopped. It also shows how the environment has changed as a result of the storm.

"A key unknown is how much dust has fallen on the solar arrays," Good said. "The HiRISE image shows some reddening of the surrounding area, suggesting dust fallout, but it is not possible to determine how much dust is on the arrays themselves."

The image comparison contains some good news: There does not appear to be an "optically thick layer of dust" that has coated this spot, Good writes. This may mean there's enough sunlight reaching Opportunity's solar panels to slowly charge its batteries.

However, no one can be sure how much dust is coating Opportunity's solar panels, or when a dust devil (a common weather phenomenon on Mars) might blow over the robot and sweep them off.

What Opportunity's possible final resting place looks like

A 3D illustration showing NASA's Opportunity rover in Perseverance Valley on Mars. Seán Doran/Flickr (CC BY-NC-ND 2.0); Business Insider

NASA's overhead images of Opportunity are revealing, but it's difficult to get a sense of what the location actually looks like.

Luckily, Seán Doran, a graphic artist who lives in the UK, has made a hobby of taking NASA's satellite imagery, maps, and other data and rendering them into realistic, from-the-surface views of spacecraft on Mars. (Doran is also known for his visualizations of Earth using satellite data, and for processing Juno spacecraft data into colorful images of Jupiter.)

On June 14 — just a few days after Opportunity went to sleep — Doran posted a realistic illustration of Perseverance Valley and the robot to show its exact location on Mars. The image, above, which Doran tweeted on Wednesday, renders the scene in color and 3D using HiRISE image and elevation data.

Doran also created black-and-white views of Opportunity, one of which is shown below. It provides a look at the robot (shown as a small white shape at center) over the valley's ridge.

An illustration of NASA's Opportunity Mars rover in Perseverance Valley. Seán Doran/FLickr (CC BY-NC-ND 2.0)

The artistic depictions give a sense of scale to Opportunity, and also a glimpse at the desolate location where the rover might rest forever.

In mid-September, as the dust storm thinned and sunlight returned to battery-charging strength, NASA began a 45-day countdown to recover Opportunity.

"If we do not hear back after 45 days, the team will be forced to conclude that the sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover," John Callas, the rover's project manager at NASA's Jet Propulsion Laboratory, said in a press release on August 30.

The deadline falls at the end of October and, if not met, would mark the end of an "active" campaign to listen for and try to contact Opportunity on a daily basis. But Callas noted the agency will still try "several months" of "passive listening" to see if the robot somehow wakes up after the deadline.

Still, the rover is more than 15 years past its warranty, and the dust storm led to one of the longest periods a solar-powered robot has ever hibernated on Mars. This could easily create a situation where some of the robot's battery or other systems suffered damage due to Martian cold and low power levels.

"Even if engineers hear back from Opportunity, there's a real possibility the rover won't be the same," NASA said in a press release in August. "No one will know how the rover is doing until it speaks."