Japan is close to becoming the 3rd nation to land on the moon in the 21st century. The US isn't one of them.

• Japan is weeks from attempting to land its SLIM spacecraft on the moon.
• If SLIM succeeds, it will become the first Japanese spacecraft to land on the moon.

On Monday, the Japan Aerospace Exploration Agency announced its SLIM moon lander had reached a crucial milestone in its historic mission: The spacecraft started to orbit the moon.

Over the next several weeks, SLIM — short for Smart Lander for Investigating Moon — will tighten its orbit, inching closer to the lunar surface.

Then, on January 19, 2024, the nation is scheduled to attempt what only a couple of other nations have achieved before it.

Japan will try to land SLIM on the lunar surface, solidifying the country's place in the history books as the third country to softly land on the moon in the 21st century. The other two countries are China and India.

When it comes to the modern moon race, the US is lagging, so far.

Japan's historic moon mission

If Japan succeeds in January, SLIM will become the first Japanese spacecraft in history to softly land on the moon.

Japan has sent a couple of impactors and orbiters to the moon in the past, but this is the first time the nation has sent a landing module with rover-like probes to explore the lunar surface in unprecedented detail.

You heard that right, probes — plural. SLIM is carrying two small probes on board. If all goes according to plan, they'll deploy from the landing module after touchdown to explore the surface beyond the landing point.

One probe uses a hopping mechanism and the other is sphere-like and changes shape to move around, per VOA news.

What makes this mission even more historic is the pinpoint landing Japan wants to achieve.

The spacecraft is targeting an impact crater on the moon called Shioli crater, and Japan plans to land SLIM to within 328 feet of its target. That's an "unprecedentedly high-precision landing," JAXA, Japan's space agency, said earlier this month.

For comparison, NASA's Apollo 17 module landed over 80 miles from its target, and India's Chandrayaan-3 lander had a target window over 3.8 square miles.

It's missions like Japan's SLIM, India's Chandrayaan-3, and China's Chang'e's 3, 4, and 5, that are pushing the boundaries of what landing on the moon looks like in the 21st century.

That leaves the US toward the back end of the pack.

The US hasn't landed anything on the moon since 1972

The last time the US landed something on lunar grounds was Apollo 17 astronauts Harrison Schmitt — the first scientist on the moon — and Eugene Cernan — the last man to walk on the moon.

In the decades since NASA has crashed some spacecraft into the lunar surface and sent others into lunar orbit.

But when it comes to landing on the moon and exploring its surface in unprecedented detail — NASA has left that for other space agencies to handle, at least for now.

To be fair, it's not like NASA isn't making giant strides in space exploration. Over the decades, NASA has landed more rovers on Mars than what India and China have landed on the moon, combined.

Moreover, NASA aims to catch up to other countries in the modern moon race in a big way very soon.

NASA's Artemis program plans to land the first humans near the moon's south pole in 2025 and achieve sustainable lunar exploration by the mid- to late-2020s.

But NASA's Artemis program has already been delayed for multiple reasons, many related to the additional complexities and costs that come with crewed missions.

Meanwhile, the main theme emerging from the modern moon race recently is building on a budget. Both Japan and India focused on building small, lightweight spacecraft to help keep costs low.

Japan's SLIM weighs 1,540 pounds (with fuel) and cost about $120 million to develop. India's Chandrayaan-3 lander weighed nearly 3,750 pounds and cost an estimated $75 million.

Will the US catch up, or will budgetary constraints, politics, and technical issues continue to hold the nation back?