What can you say about Elon Musk that hasn’t already been said? The eccentric billionaire sounds more like a James Bond villain than a philanthropic tech genius (sans the villainy part . . . we hope). Not one to rest on his laurels, Musk has given new meaning to ‘March Madness’ with his lofty goal of getting people on Mars by 2019, which would incidentally mark the 50th anniversary of the first Moon landing by the late Neil Armstrong in 1969. Not to be outdone, Vladimir Putin himself has planned to put Russians on Mars by 2019 as well. (Space Race 2.0, anyone?)

How does this relate to green energy? It all starts with the rocket technology. You’d have to be living under a moonrock to not have heard about SpaceX's Falcon Heavy rocket that propelled a Tesla Roadster into orbit. The audacious stunt, carried out in early February this year, shows that Musk’s faith in reusable-rocket tech is unwavering. Of course, for most of history, rockets were a one-and-done kind of deal. Naturally, such waste meant that the price per kilogram of cargo payload was (ahem) astronomical.

As it turns out, reusing rockets is also greener than an Irishman on St Patrick’s Day, which is due to drastic reduction in total construction emissions. Fully reusable launch vehicles are crucial for another reason: they are practical for return journeys from Mars, both in terms of safety and cost.

Musk’s mission to get humans to Mars by the end of 2019 is only conceivable because of significant advances in various scientific disciplines. Obviously, Musk hopes to send people there to live indefinitely, not to be stranded there until they run out of resources. To that end, Musk has often joked over the years regarding the colonization of Mars: “I would like to die on Mars. Just not on impact.”

Making a one-way trip to Mars without the need for long-term habitation is a lot less complicated than having to make the first human contact with an alien planet while also establishing a settlement and/or embarking on a rapid return journey. This is where the green-energy aspect to this mission kicks in. But before I cover how a Mars settlement is powered on Martian soil, let’s take a look at solar energy on Earth.

Solar power on Earth has come a long way. Alexandre Edmond Becquerel famously observed the photovoltaic effect via an electrode in a conductive solution exposed to light back in 1839. It wasn’t until the late 1800s, however, that various solar-related patents would be filed, including the terms ‘Solar cell’ and ‘solar storage’ in 1888 and 1899, respectively. It wasn’t until the mid-1950s, though, that Bell Labs would manufacture solar cells for, funnily enough, space activities.

Throughout the decades—as with the prices of computer processors—the cost-per-watt status of solar cells plummeted. In a way, Swanson’s law is the solar equivalent of Moore’s law for computing. While the effect of Swanson’s law has not being as dramatic as Moore’s law (which has caused computing power to roughly double every two years since the law was first invoked in 1975), the effect is still remarkable. For the past half a century, the cost per watt has fallen 10% each year. While that might not sound too dramatic, keep in mind that such a trend means the price has gone from $76.67 per watt in 1977 to as little $0.46 per watt in 2017; Chinese markets were purported to get as low as $0.36 per watt in 2014. Solar energy is so efficient, in fact, that the only other energy source that beats it is wind, narrowly eclipsing at $0.30 per watt under optimal conditions (with $0.60 being a high-end estimate).

In the next part of this three-part article, I’ll explain why solar energy on Mars will likely face a serious problem (as well as the other energy source that might usurp it). Please feel free to follow me to make sure you catch part 2 and part 3!