NASA scientists have successfully received a transmission from the Mars Opportunity rover - a positive sign despite the worsening dust storm that has left science operations on the red planet suspended. Data from the transmission let engineers know the rover still has enough battery charge to communicate with ground controllers at NASA's Jet Propulsion Laboratory in the US. The transmission received this week was especially good news considering the dust storm has intensified in the past several days. A dark, perpetual night has settled over the rover's location in Mars' Perseverance Valley, NASA said in a statement. The storm's atmospheric opacity - the veil of dust blowing around, which can blot out sunlight - is now much worse than a 2007 storm that Opportunity weathered. Opportunity's team has requested additional communications coverage from NASA's Deep Space Network, a global system of antennas that talks to all the agency's deep space probes. This latest data transmission showed the rover's temperature to be about minus 29 degrees Celsius. One saving grace of dust storms is that they can actually limit the extreme temperature swings experienced on the Martian surface. The same swirling dust that blocks out sunlight also absorbs heat, raising the ambient temperature surrounding Opportunity. Engineers will monitor the rover's power levels closely in the week to come. The rover needs to balance low levels of charge in its battery with sub-freezing temperatures. Its heaters are vitally important to keep it alive, but also draw more power from the battery. Likewise, performing certain actions draws on battery power, but can actually expel energy and raise the rover's temperature. The rover has proved harder than expected by lasting nearly 15 years, despite being designed for a 90-day mission. NASA's Mars Reconnaissance Orbiter first detected the storm on June 1. As soon as the orbiter team saw how close the storm was to Opportunity, they notified the rover's team to begin preparing contingency plans. In a matter of days, the storm had ballooned. It now spans over 18 million square kilometers and includes Opportunity's current location at Perseverance Valley. This is not Opportunity's first time hunkering down in bad weather: in 2007, a much larger storm covered the planet. That led to two weeks of minimal operations, including several days with no contact from the rover to save power. The project's management prepared for the possibility that Opportunity couldn't balance low levels of power with its energy-intensive survival heaters, which protect its batteries from Mars' extreme cold. It is not unlike running a car in the winter so that the cold does not sap its battery charge. There is a risk to the rover if the storm persists for too long and Opportunity gets too cold while waiting for the skies to clear. Ultimately, the storm subsided and Opportunity prevailed. The Martian cold is believed to have resulted in the loss of Spirit, Opportunity's twin in the Mars Exploration Rover mission, back in 2010. Despite this, both rovers have vastly exceeded expectations: they were only designed to last 90 days each. Opportunity is in its 15th year; the team has operated the rover for more than 50 times longer than originally planned.