We may be on the verge of solving the mystery of the Martian moons. On 20 October, the Martian Moons eXploration (MMX) spacecraft launches towards the larger of the two moons, Phobos, with the goal of bringing back a sample that may finally explain how Phobos and its sibling, Deimos, formed.

MMX will launch from Tanegashima Space Center in Japan. If all goes to plan, it should arrive at Mars in August 2027, entering an orbit that keeps it alongside Phobos so it can build a detailed map of the surface. Along the way, it will also observe the surface of Deimos.

Once the map is complete enough, the spacecraft鈥檚 operators at the Japan Aerospace Exploration Agency (JAXA) will use it to pick out a spot on Phobos for MMX to land. During one or two brief landings, it will take on two tasks: to drop off a small rover called IDEFIX and to pick up samples. The rover is the first anyone has ever placed on such a small cosmic body, so part of its purpose aside from scientific observations is to confirm that a wheeled rover even works on an object with such low gravity.

The samples, though, are the most important part of the mission. MMX has two different sampling devices: one that shoots a puff of gas onto the surface, blowing dust and pebbles back up into a sampling container, and another that blasts a hollow cylinder into the ground to take a sample a several centimetres deep. After the samples are taken, they will be stowed away inside the spacecraft, which will then head back towards Earth. It is expected to arrive home in 2031.

Once these samples get back to Earth and are analysed by scientists on the ground, they should finally solve the mystery of how Phobos and Deimos formed. For more than a century, researchers have debated whether the two are captured asteroids or formed from an impact on Mars, similar to how Earth鈥檚 moon formed. On first look, their shapes and surfaces resemble asteroids, but their circular orbits around Mars鈥檚 equator are more consistent with the impact hypothesis. Figuring out what they are made of should settle it once and for all.

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This will also help illuminate what the solar system was like billions of years ago when these strange moons formed. 鈥淗aving the answer will help illuminate that early era when Earth and the other inner planets may have been acquiring much of their water and organic compounds,鈥� said , part of the NASA team that is collaborating on the MMX mission, in a .

If we are very lucky, the samples from Phobos may even contain bonus bits of dust and debris from Mars itself. Impacts on the planet could have launched material into space, which would have collected on the moon鈥檚 surface and been preserved there for billions of years. That means that these samples could illuminate not just the history of Phobos and Deimos, but also of Mars.

A newly formed crater on the moon is teaching us about our nearest neighbour鈥檚 complex geology. The crater, formed by an asteroid impact in 2024, is the largest that we鈥檝e ever watched form in real time.

It was first spotted last year, when researchers compared sets of images taken by in both 2024 and 2025, and was named McGetchin crater. According to models of how often impacts occur on the moon, one this big 鈥� about 222 metres across 鈥� is only expected to occur about once every 132 years.

While the moon has many larger craters, watching one as it forms and evolves presents a unique opportunity to learn about the lunar surface and its geology. 鈥淐ratering is probably the most common process that happens in the solar system, so we spend a lot of time trying to understand how a new crater will modify a surface and watching that degrade over time,鈥� says at Johns Hopkins University in Maryland. 鈥淗aving a baseline for a pristine crater that can serve as our calibration point for how these processes start is really incredible.鈥�

Powell and his colleagues measured the surface temperature in the region around McGetchin crater, and found that the impact had formed a spot about 7 kilometres wide that is a handful of degrees colder than the rest of the area during the lunar night. These cold spots form when the lunar dust fluffs up after an impact, so it cools down faster after the sun sets.

Another team, led by at Intuitive Machines in Texas, found that the impact flung dust and rocks more than 120 kilometres from the crater itself. 鈥淥ver the last several years, we鈥檝e developed this understanding that these impacts modify more than just the region right where the crater is,鈥� says Powell. 鈥淚t鈥檚 really striking that a crater can modify the lunar surface to distances far larger than the crater itself.鈥�

This will helps us understand and study the history of the moon and other airless, cratered objects in the solar system, but it could also aid in future exploration. 鈥淚f we鈥檙e trying to send rovers or astronauts or build things on the moon, we want to understand the properties of the surface,鈥� says Powell. And watching a huge new crater form and change over time is one of the best remote probes of the surface we鈥檝e ever had.

Venus has no moon, but a modelling study suggests it probably did have one for nearly 2 billion years 鈥� before the planet ate it. Understanding this could help us learn about Venus鈥檚 previous habitability.

Many large objects probably hit Venus in the early solar system, which could have formed a moon, similar to the giant impact that is thought to have formed Earth鈥檚 moon. 鈥淭here鈥檚 a very good chance that Venus did have a moon-forming impact,鈥� says at the University of California, Riverside.

The lack of a moon today is therefore quite unusual, but Kane and his colleagues might have an answer. They modelled what would have happened if Venus did have a moon, and found that in almost all scenarios, it would have been consumed by the planet, long erased from existence by the present day.

Venus rotates quite strangely with respect to the sun, completing a rotation once every 243 days, compared with its orbit of 225 days. This is possibly a result of its thick atmosphere slowing its spin.

In contrast, Earth鈥檚 much faster spin transfers angular momentum to our moon, meaning it is moving away a few centimetres each year. For Venus, the opposite would have been true. 鈥淭he moon is transferring angular momentum inward instead of outward,鈥� says Kane. 鈥淚t causes the moon鈥檚 orbit to catastrophically collapse.鈥�

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The researchers found that at the upper limit of their models, a moon about half the mass of our own could have survived around Venus for 1.7 billion years. At twice the mass of our moon, it would have survived just 30 million years, because of the stronger tidal effect.

Once the moon reached a distance of about 15,000 kilometres, it would have encountered a boundary known as the Roche limit. 鈥淭hat鈥檚 where Venus鈥檚 gravity rips the moon apart and consumption occurs,鈥� says Kane, with the moon鈥檚 debris temporarily forming a ring around Venus until it fell into the atmosphere.

at Washington University in St Louis, Missouri, says the model is interesting but hard to prove. 鈥淚t鈥檚 exceedingly hard to test this idea because there is basically nothing left behind.鈥� This is because Venus鈥檚 surface has been repeatedly resurfaced by volcanism, he says.

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Kane, however, says a future mission to the surface of Venus could include a seismometer, a device that measures seismic waves to study the interior of the planet. This could look for evidence of a consumed moon buried underground. 鈥淭hat would tell us a lot,鈥� he says.

If Venus did have a moon, it may have played a role in the planet鈥檚 habitability, with Venus once thought to have had oceans on its surface. It is possible a moon could be linked to the planet鈥檚 runaway greenhouse effect, in which it lost all its water for reasons unknown and developed a thick, deadly atmosphere.

鈥淚f there was an early habitable period of Venus, then the big question is what brought that to an end,鈥� says Kane. A moon crashing into the planet could have evaporated much of its water. 鈥淚t could definitely be connected to Venus鈥檚 runaway greenhouse state,鈥� says Kane.

Part of a discarded SpaceX rocket is believed to have crashed into the moon at 8700 kilometres per hour earlier this morning. Astronomers around the world trained their telescopes on the predicted site of the impact in the hope of capturing images and eking some useful science out of the accidental collision.

The craft is the upper stage of a SpaceX Falcon 9 rocket that launched in January last year carrying the Hakuto-R spacecraft from commercial company ispace 鈥� which, ironically, also crashed into the moon during an unsuccessful landing attempt.

It is thought that the almost 14-metre-long, 4000-kilogram Falcon upper stage impacted the moon at 5.35am BST today. The crash was predicted to occur close to Einstein crater, which would place it towards the edge of the visible moon from Earth.

at the University of Leicester, UK, says that telescopes around the world were trained on the site of the impact and that images of the area before and after impact will emerge soon. Lunar orbiters from South Korea and the US will also observe the impact site.

NASA predicts that the impact will have created a crater that is 18 metres wide and 4 metres deep.

鈥淚t is not a good thing to be randomly sending debris into the moon,鈥� says Sargeant. 鈥淚t鈥檚 not something we should be making a habit of. What if it hit a site of special interest? What if it caused damage to the historical Apollo landers?鈥�

Both NASA and the European Space Agency are required to take the end of a spacecraft鈥檚 life into account before a mission launches, ensuring that there is a plan and enough fuel to safely deorbit it. Commercial companies aren鈥檛 covered by the same rules, says Sargeant, although efforts to introduce such requirements are under way.

When SpaceX launched the Falcon in question, the heavy payload required more thrust than usual, meaning that the rocket ended up floating uncontrollably in space. It eventually fell into an orbit that unintentionally put it on a collision course with the moon.

But Sargeant says that some science can be salvaged from the event, with astronomers likely to capture rare images of a moon crater being created and the lunar regolith plumes ejected from the impact.

at the Macau University of Science and Technology, China, says that all planetary surfaces should ideally be kept as pristine as is feasible 鈥� without hindering exploration 鈥� but that the moon has already been impacted by decades of US, Soviet and Russian, Chinese, Indian, Israeli and other nations鈥� missions, as well as millions of years of asteroid impacts.

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鈥淩ockets have been landing, crashing and taking off from the surface for decades now,鈥� says Bugiolacchi. A controlled crash may even be welcomed by planetary scientists, he says. 鈥淜nowing the projectile鈥檚 mass, impact velocity, angle and trajectory provide invaluable data on surface evolution. The primary agent shaping most planetary surfaces is high-velocity impacts. Normally, these events are entirely random in terms of physical properties and dynamics.鈥�

鈥淭he moon already has about 100 million natural impact craters of the size expected to be made by this crash, so such a crash will hardly make a difference,鈥� says at the Open University, UK. 鈥淚鈥檇 be happy with a deliberate collision into the moon if it were done with a science aim and was set up so as to be studied to learn about the moon鈥檚 interior or surface composition. However, this crash is accidental and reckless.鈥�

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Titan鈥檚 plains may be covered in up to a metre of fluffy, organic 鈥渟now鈥�. About 65 per cent of the surface of Saturn鈥檚 huge moon is made up of strangely uniform and flat plains, and they seem to be coated in a porous, dry layer of particles that have fallen from the sky.

The surface of Titan is difficult to study from afar because it is obscured by a thick, hazy atmosphere. The Cassini spacecraft, which orbited Saturn from 2004 to 2017, managed to take a closer look using radar. Now, at Cornell University in New York state and his colleagues have analysed the radar data in more detail than ever before.

The way the radio waves from Cassini鈥檚 radar instrument bounced off Titan鈥檚 surface indicate that the surface isn鈥檛 as simple as those of most other rocky bodies in the solar system. 鈥淭he canonical models that we use to try to understand Titan鈥檚 surface, which were developed for the moon and are used for the moon, Earth, Venus 鈥� they don鈥檛 work directly on Titan,鈥� says Hayes. 鈥淭itan is a different beast in terms of the radar-scattering properties of the surface.鈥�

Instead of a simple rocky surface, the radar data was a better fit to a two-layer model, with a blanket of soft, low-density material covering a harder terrain. The blanket layer, ranging from centimetres to a metre in thickness, is probably made up of organic molecules from Titan鈥檚 hazy atmosphere, which researchers expect should float down to the surface like snow before getting compacted and solidified over time.

Titan鈥檚 surface also experiences rain, wind and erosion, so it is important to understand how the blanket layer has built up slowly over time, shaped by these processes. 鈥淏ut this could give us a hint for how things work more broadly on Titan,鈥� says Hayes.

NASA鈥檚 Dragonfly mission, which is expected to launch in 2028 and arrive on Titan in 2034, should be able to measure these layers and help us figure out exactly how they formed. It is crucial not only for our understanding of Titan itself, but also for the design of any future spacecraft that will follow Dragonfly to visit this strange moon and attempt landing there.

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