The race to become the first private entity to land a robot on the Moon is heating up, as five teams close in on the Google Lunar XPrize. The final heat of candidates were winnowed down from dozens of contenders that couldn’t clear hurdles or meet deadlines for the prize, which included designing and building original spacecraft, meeting flight regulations, and securing a launch contract scheduled to blast off by the end of 2017.

The last groups standing were announced on Tuesday: They are (drum roll) Moon Express, SpaceIL, Team Indus, Hakuto, and Synergy Moon. All five teams are tentatively on track for launches this year.

Established in 2007 by the nonprofit XPrize organization, the Google-sponsored Lunar XPrize is an open challenge to create a robot that can voyage to the Moon, travel at least 500 meters on its surface, and send high-resolution visuals back to Earth. A total of $30 million in prize money is at stake, two thirds of which will be awarded to the first team to successfully meet the contest’s requirements.

The impetus for the Lunar XPrize was to stimulate innovation in the global space community, and by that standard, the contest is already successful. The hopeful companies advancing into the 2017 home stretch have wildly different lunar exploration strategies and goals, plus they hail from all around the world. Here’s a quick rundown of the five penultimate lander concepts.

Animation of MX-1E landing on the Moon. Image: Moon Express

Moon Express: MX-1E Lander

Moon Express, a Florida-based company founded in 2010, is the first private entity to be granted clearance to land on the Moon, an achievement it hopes to build on by putting its MX-1E Lander on the lunar surface as soon as possible. The company has a launch contract with Rocket Lab, a US aerospace venture with launch facilities in New Zealand. Their lander is expected to hitch a ride on that company’s lightweight Electron rocket at some point this year, after the Electron has been adequately flight-tested.

READ MORE: How the First Private Moon Landing Will Spur the Future of Space Mining

The MX-1E represents a significant departure from the traditional “lab-on-wheels” lunar rovers deployed by the American, Russian, and most recently, Chinese space programs. Instead of driving around, the robot will leverage the Moon’s weaker gravity well by executing controlled hops to various locations on the surface.

"Why crawl when you can fly?"

“Why crawl when you can fly?” a Moon Express spokesperson told me over email. “Although rovers have an important place in planetary surface exploration, our business model is to provide lunar access to a wide variety of locations on the Moon.”

Indeed, Moon Express has long-term aspirations to establish mining operations on the Moon and other celestial bodies, so it makes sense for them to focus on vehicles that can examine and prospect several sites over vast areas.

Sparrow model on display in 2015. Image: אמא של גולן/SpaceIL

SpaceIL: Sparrow

The Sparrow lander, developed by the Israeli nonprofit SpaceIL, takes the cake for the most futuristic design concept in play for the XPrize. With its spindly legs and funnel-shaped bus, the spacecraft looks completely different from past lunar rovers. Like the MX-1E, it is designed to hop from place to place, which team leads say will conserve mass and gas relative to its rival rover concepts.

SpaceIL has brokered a contract with SpaceX, and is on track to be bundled into a Falcon 9 rocket launch at some point in 2017. The project was largely developed and executed by volunteers, and the team leads have pledged to invest most of the XPrize to educational programs should they win it.

Concept art of Tesla rover. Image: Synergy Moon

Synergy Moon: Tesla Rover

Synergy Moon is a diverse collective of specialists spanning 15 nations, and is working on developing “at least one rover” in its Tesla series, illustrated above, according to its XPrize page. The rovers are equipped with two identical cameras that provide stereoscopic vision. Synergy Moon aims to make its high-definition view of the Moon to be accessible to anyone online. The group has arranged its launch through Interorbital Systems’ Neptune rocket.

ECA Rover mockup. Image: TeamIndus

TeamIndus: ECA Rover

TeamIndus, a for-profit spaceflight company based in New Delhi, is shooting to land its adorably anthropomorphic 11-pound rover, currently codenamed ECA, in the Moon’s Mare Imbrium region. The team has already won a $1 million Milestone award for its landing technology.

For launch arrangements, the company is joining forces with one of its XPrize rivals, the Japanese group Hakuto. The two teams have arranged to bundle both their landers into the same PSLV rocket, a model developed by the Indian Space Research Organization. The launch is currently scheduled for late December 2017.

Prototypes of Hakuto rovers. Image: Hakuto/XPrize Foundation

Hakuto: Moonraker and Tetris Rovers

Last but certainly not least, meet the Moonraker and Tetris dual rovers developed by the Sendai-based Hakuto. The two-wheeled Tetris is designed to be tethered to the four-wheeled Moonraker like a trailer, which will enable it to be lowered into so-called “skylights” on the Moon. The lunar surface is thought to be riddled with underground caves, tunnels, and basaltic lava tubes, some of which may be accessible through skylight channels. The Hakuto team aims to be the first to explore these tantalizing lunar realms with its unique roving tag-team.

These diverse and innovative concepts herald a crucial turning point in lunar surface operations, which have been on hold since the 1970s (with the notable exception of China’s Yutu rover, deployed in 2013). Previous mobile robots sent to the Moon by the Russia, China, and the US were primarily tasked with studying the alien environment, and to occasionally blast back samples of lunar rock. All of them bundled scientific instruments into a traditional rover design.

The XPrize finalists have broken out of that mould in a few significant ways. Moon Express and SpaceIL may demonstrate that hopping around on alien bodies is a promising alternative transportation method to driving over terrain. This could have big repercussions for future missions to the Moon, Mars, and beyond, especially if hoppers can reliably clear hurdles, like cliffs or extreme terrain, that rovers must avoid.

“Rovers are very slow and cannot travel significant distances,” the Moon Express team told me. “Our robotic spacecraft can re-launch and fly to distant locations for science and exploration diversity. We can deploy rovers in each location—consider the advantage of multiple landings for a single launch.”

"We can deploy rovers in each location—consider the advantage of multiple landings for a single launch."

More broadly, the smorgasbord of objectives and design concepts each team has put forth shows that private groups can greatly diversify avenues of space exploration over a relatively short timespan. Impressively, many of these companies are less than a decade old, and some are based in countries that have never ventured to the Moon before.

It’s difficult to predict which finalist will end up snagging the winning $20 million prize, and at this point, much of it is up to luck. If the novel Electron and Neptune rockets require further testing, or if SpaceX needs to alter its launch manifest for some reason, the teams relying on those vehicles will be held up through no fault of their own.

That said, the fact that these teams have gotten this far distinguishes them all as pioneers. While one of them will likely succeed in cinching the honor of being the first non-governmental group to land on the Moon, explore it, and send back pictures, the runners-up no doubt earn a shout-out in the history books as well.