NASA and other government employees working on a space programme have been exempted from the ongoing US government shutdown.

Despite the furlough of 97% of NASA’s roughly 18,000-strong workforce, employees working on the Mars Atmosphere and Volatile Evolution (MAVEN) programme, including launch, have been declared essential to the functioning of government.

While perhaps not the most crucial of programmes, MAVEN owes its continuity to orbital mechanics. The scheduled launch window, lasting from 18 November into early December, is one of the few prime opportunities to launch an object from Earth on a path to Mars that requires the least amount of energy. Should the launch date be missed, the spacecraft would have to be stored until 2016 at the earliest.

The rest of NASA remains on hiatus until the US government passes a spending bill, appropriating money to run government functions.

Should MAVEN launch successfully, the spacecraft will enter into a highly elliptical Martian orbit in mid-2014, dipping in and out of the planet’s thin atmosphere to study the particles therein. Though Mars once had an Earth-like atmosphere, it dissipated for unknown reasons; researchers hope studying the current atmosphere will shed light on how the planet evolved.