It is the refrain of teachers everywhere preparing their students for standardised tests: “Make an educated guess.” An answer is always better than no answer, they say, and if you can apply what you know to the question to rule out some of the choices, even better. Of course, scientific research isn’t a multiple-choice exam, and its bedrock is the idea that an educated guess without solid evidence just isn’t good enough. But the concept is still a useful one, particularly when our questions outpace the technology we currently have to answer them.

The key part of the phrase “educated guess” is the first word. Put another way, a guess based on nothing may be worse than no guess at all. “But Leah,” I hear you asking, “Do you have a framework, or a favourite example, for educated guesses?” And just because you are clamouring for it, and I’m the kind of person who has favourite equations, I will tell you about it. The Drake equation, which turns 65 years old next month, is an incredibly useful tool for framing our thinking about life in the cosmos – even though, at its core, it is simply a method for making an educated guess.

Astrobiologist Frank Drake came up with his eponymous equation in 1961, before convening the first scientific conference on the search for extraterrestrial intelligence (SETI). According to written by his daughter, science journalist Nadia Drake, he sketched out the equation on a bit of a whim to get the few attendees of the meeting talking and was, even into his later life, astonished by how important it is now considered.

The equation has seven key terms, and when multiplied together, they provide an estimate of N: the number of intelligent civilisations in the Milky Way galaxy with whom we might someday be able to communicate. It looks like this:

N = R_* × f_p × n_e × f_l × f_i × f_c × L

The first few terms are relatively simple. R_* is the rate of star formation in our galaxy, which has been measured at about 1 to 3 stars per year. The fraction of those stars with planetary systems is f_p, and we now think that number is about 1 as well – most stars seem to have planets. The number of planets per star with an environment suitable for life is n_e, and that is where things start to get more complicated. “Suitable for life” is a broad idea, and one that’s difficult to define. Even the most basic requirement – that the planet be in its star’s habitable zone, where temperatures allow liquid water on the surface – is required for Earth-like life, as far as we know, but it’s certainly possible that other lifeforms have different needs. In our own solar system, there are either 2 or 3 planets in the habitable zone, depending how you slice it – but Venus and Mars don’t seem particularly suitable for life, and there are several moons in the outer solar system that may well be.

That is the first time the equation forces us to make an educated guess. The second comes hot on its heels with f_l, the fraction of the habitable planets that go on to develop life. On this, we have an even smaller sample size. We haven’t found life anywhere but Earth, so this number could be very small, or it could be 1 – remember, this includes life that arises at any point in the history of the cosmos. But until we do find life elsewhere, it will be more of a philosophical argument than anything else. The same is true of the next two terms of the Drake equation: f_i, which denotes the fraction of life that is intelligent – the definition of which is also wily – and f_c, the fraction of intelligent lifeforms that eventually broadcast their existence into space and are thus capable of communicating with us. The final term is L, the length of time in which a civilisation of intelligent lifeforms sends detectable signals out into space. As the astronomer Carl Sagan pointed out, this depends heavily on whether such civilisations can avoid self-destruction, which isn’t something we can know for sure – but we make our best guess based on the only evidence we have: human history.

If you combine all the lowest estimates, N could be one-trillionth or even lower, implying that we are totally alone in our galaxy. If you combine the highest estimates, there could be tens of millions of civilisations in the Milky Way that we could communicate with, which to me would say it’s only a matter of time before we find them. At Drake’s original SETI meeting, the researchers set N between 1000 and 100,000,000, and the lower end of that sounds about right to me – an estimate that, like those at the meeting, is based largely on my not-particularly-scientific opinions about how long our civilisation might last.

But when it comes down to it, the number itself isn’t the important part of the equation; the important part is the process of estimating each of its terms. In doing so, we force ourselves to consider some of the biggest questions in science: How similar are other places in the universe to our own cosmic neighbourhood? How likely are those most-similar places to develop life? What is life, anyway? What does life truly need? What is intelligence? How can we search for it? And how long will we be capable of searching for it? None of those questions are answered definitively, but pondering them can help us direct our scientific research – and more than that, it gives us an idea of our place in the grand scheme of the universe. That’s why teachers tell their students to make an educated guess, and it’s why the Drake equation is still considered so important. The value in an educated guess is in taking account of what you know and what is still out there, waiting to be known.

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’s 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’s moon formed. On first look, their shapes and surfaces resemble asteroids, but their circular orbits around Mars’s 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. “Having 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,” 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’s 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.

The astonishing diversity of the cosmos is on display in the 2026 Astronomy Photographer of the Year competition, organised by the Royal Observatory in Greenwich, London. From our own solar system to distant nebulae, these images showcase the many wonders we can observe from the ground on Earth.

The overall winner (above), The Quiet Predator, was taken by Ali Alobaidly in Kuwait. It shows a dense nebula 650 light years away, in the constellation Cepheus. This cloud of dust, called the Shark nebula, contains a few bright stars that make their surroundings glow blue. The nebula is so dark and distant that it took Alobaidly more than 28 hours of observing to create this image.

The runner-up in the competition (above) is Beyond the Wormhole, taken by Kfir Simon in Israel. While the image may evoke a hole in space-time, it actually depicts the centre of the Helix nebula, which is about 650 light years away in the constellation Aquarius. Beyond the central star that formed the nebula when it shed its outer layers thousands of years ago, extraordinarily distant galaxies shine through the dust and gas.

In the Our Moon category, Venusian Pearl on the Moon (above) took the prize. Petr Horalek took this photograph in the Czech Republic as the moon passed in front of Venus in the middle of the day. He captured this relatively rare event, called an occultation, just as Venus slipped behind the crescent moon.

The runner-up in the Our Sun section is, unsurprisingly, an image of the sun. However, Anatomy of the Chromosphere (above), captured by Peter Ward in Australia, isn’t a simple photograph. It represents two different wavelengths of light, one of which captures emission from hydrogen along the sun’s edges, represented in red, while the other shows emission from calcium, shown in lilac. Together, they reveal the structure of the sun’s chromosphere, which is the layer just above its visible surface, but below its corona.

Comet C/2025 A6 (Lemmon) jets across the sky in this highly commended image by Julien DeWinter and Landon Boehm, taken from Texas. When it was captured, in October 2025, the comet was almost at its closest point to the sun, about 101 million kilometres from Earth. That proximity to the sun caused remarkable activity on the comet, creating two long plumes, one made of dust and the other of electrically charged plasma.

With a more earthly setting, the winner of the Skyscapes category is Botswana Star Trail, taken by Stefano Pellegrini. It captures the movement of stars above a grove of baobab trees over the course of 340 camera exposures, each lasting 30 seconds.

The winning images from the competition will be exhibited at the National Maritime Museum in London from 18 September.

A newly formed crater on the moon is teaching us about our nearest neighbour’s complex geology. The crater, formed by an asteroid impact in 2024, is the largest that we’ve 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 – about 222 metres across – 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. “Cratering 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,” says at Johns Hopkins University in Maryland. “Having a baseline for a pristine crater that can serve as our calibration point for how these processes start is really incredible.”

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. “Over the last several years, we’ve developed this understanding that these impacts modify more than just the region right where the crater is,” says Powell. “It’s really striking that a crater can modify the lunar surface to distances far larger than the crater itself.”

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. “If we’re trying to send rovers or astronauts or build things on the moon, we want to understand the properties of the surface,” says Powell. And watching a huge new crater form and change over time is one of the best remote probes of the surface we’ve ever had.