The U.S. military must be ready to engage the enemy farther from home than ever before, according to its highest-ranking officer.

"Today's modern battlefield operates from the seabed to cislunar space," Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, said Wednesday (Sept. 16) during a keynote address at the Air & Space Forces Association's Air, Space & Cyber Conference in National Harbor, Maryland.

Cislunar space extends from Earth all the way out to the orbit of the moon and includes the lunar surface. For several years now, military officials have been stressing the strategic importance of this huge region, which could get quite a bit busier in the next decade or so.

For example, both the United States and China plan to build bases near the moon's south pole, which is thought to harbor large amounts of water ice. Winning this new moon race is critical, U.S. officials have stressed, because whoever does so will be able to establish norms of behavior on and around Earth's nearest neighbor.

China has already demonstrated impressive capabilities in the lunar sphere. In 2019, the nation's robotic Chang'e 4 mission pulled off the first-ever soft landing on the moon's mysterious far side. In 2024, Chang'e 6 returned far-side samples to Earth — another first.

Caine didn't cite such missions or even mention China by name. And he provided no details about what conflict on the cislunar battlefield might look like (though presumably it would be entirely robotic, with satellites seeking to take out adversary craft via jamming or blinding).

But he invoked the cislunar battlefield twice and noted that U.S. military branches cannot assume continued dominance of their various domains.

"Future conflicts will demand that we operate without the assumptions of uncontested access, secure rare areas or uninterrupted or uncontested sustainment," Caine said. "Our task, my friends, is to adapt right now, so the joint force is prepared to fight, endure and win in global contested environments, from the seabed to cislunar space."

The United States' long-held advantage in the final frontier will be key to securing such victories, he added.

"We must continue to ensure that the United States of America can strike anywhere on the globe at the time and place of our choosing, and sustain that force," Caine said. "Our United States Space Force must provide unrivaled space superiority and sustain the associated networks, domain awareness [and] data advantage that the joint force needs to win in space, both now and in the future."

We now know that part of the Space Force's strategy for maintaining that crucial superiority is the operation of weapons in Earth orbit. The branch's chief, Gen. Douglas Schiess, admitted as much during an address at the same conference on Tuesday (Sept. 15).

"Let me be crystal clear: Today, guardians operate on-orbit weapons that can defend the joint force against space-enabled attacks,” Schiess said during his speech. ("Guardian" is the official name for a member of the Space Force, just as members of the U.S. Navy are called sailors and members of the Army are soldiers.)

Schiess provided few details about these weapons but, later in the speech, implied that they are electromagnetic rather than kinetic in nature. That is, they're probably designed to knock out key systems of adversary satellites rather than destroy the entire spacecraft (which would create a cloud of potentially troublesome debris).

It's no surprise the U.S. possesses and employs such technology; the newsworthy bit is that a top official said it so openly. The nation's chief rivals in the space domain, China and Russia, possess advanced counterspace technologies as well. For example, both have destroyed defunct satellites with missiles and conducted close approaches of spacecraft with "inspector" vehicles.

The rings around a strange small body orbiting between Saturn and Uranus look mysteriously different from previous views, new observations from the James Webb Space Telescope (JWST) suggest.

The rings encircle Chariklo, which is a centaur, a strange type of object that shows characteristics of both asteroids and comets. Chariklo is only about 400 miles (250 kilometers) in diameter and is part of a large group of tiny objects in the distant solar system.

Scientists first discovered Chariklo's rings in 2013 — making it the first small solar system body found to have rings — and studied them with ground-based telescopes again in 2014 and 2017. When JWST took another look at Chariklo in 2022, a decade had brought a lot of difference, according to a study published Sept. 9 in the journal Science Advances.

"By comparing JWST observations with those obtained … over the last decade, we discovered opposite changes in the two rings: while the inner ring shows significantly higher opacity, the outer ring shows lower opacity, " Pablo Santos-Sanz, a researcher at the Institute of Astrophysics of Andalusia and first author of the study, said in a statement.

Researchers don't know exactly how the changes took place, but the study authors offered three suggestions. The first is that JWST, which has a fine resolution, was able to see both denser and sparser zones of the rings than previous observations showed. The second is that there were changes in the rings' material or in the grains themselves. Finally, a third possibility is that JWST could see "grains with wavelength-dependent optical properties," meaning the telescope saw effects in composition and grain size that explain the variability.

Santos-Sanz said the research suggests that small bodies with rings — even those orbiting far away from the gravitational influences of planets — may have more changes in their systems than scientists previously thought. "Our results force us to rethink how they form, how they evolve, and what mechanisms maintain their stability," he said.

A theoretical follow-up observation, taken the next time Chariklo passes in front of a star, would help to confirm the new JWST results, the researchers added — especially the apparent decreased opacity of one of the rings and the increased opacity of the other.

"These observations would help disentangle temporal evolution from wavelength-dependent scattering effects, and clarify the physical processes shaping Chariklo’s rings," the researchers stated in the study.

A JWST milestone

The new observations of Chariklo also mark the first time that scientists have planned a JWST viewing campaign specifically around a stellar occultation — that is, the researchers timed the viewing precisely to when Chariklo passed in front of a distant star from the telescope's point of view.

All observations of Chariklo's rings, on the ground and in space, have used stellar occultations. That's because the rings are too faint to be imaged directly, so astronomers must instead learn more about the rings by measuring the dips and increases in brightness as Chariklo passes in front of the background star. Scientists use a similar method to study the atmospheres of alien planets with JWST's infrared instruments.

Chariklo's speed relative to JWST was low, at 1.5 miles per second (2.5 kilometers per second), allowing for fine imaging of the rings. To time the occultation, the researchers used info from the European Space Agency's Gaia mission, which precisely charts the locations and movements of more than 2 billion stars, as well as calculated the orbit of JWST at a location roughly 930,000 miles (1.5 million km) from Earth in the opposite direction of the sun. According to the researchers, the planning and execution of the mission required "extreme precision."

For years, the idea of nuclear weapons in space sounded more like science fiction than a realistic threat. That changed Monday (Sept. 14), when U.S. Air Force Secretary Troy Meink announced at the Air, Space and Cyber Conference in Maryland that the U.S. had deployed "on-orbit space control weapons capable of defending the Joint Force against hostile adversary action."

While the officials have not said that these weapons are nuclear, the announcement has raised a question: If countries are now openly putting weapons in space, how far away are we from a future where nuclear weapons become part of that competition?

The concerns about nukes in space goes back to the 1960s. In 1967, the U.S. and the Soviet Union signed the Outer Space Treaty, in which the nations agreed to not place nuclear weapons or other weapons of mass destruction in orbit around Earth. But this treaty never included an enforcement mechanism — and now, that tenuous compromise may have been violated entirely, inviting other countries to add their own weapons to the final frontier.

With the U.S.' recent announcement, are you worried about an arms race in space? Vote in our poll below, and leave your thoughts in the comments.