A mystery interstellar object discovered last week is likely to be the oldest comet ever seen – possibly predating our solar system by more than three billion years, researchers say. The "water ice-rich" visitor, named 3I/ATLAS, is only the third known object from beyond our solar system ever spotted in our cosmic neighbourhood and the first to reach us from a completely different region of our Milky Way galaxy. It could be more than seven billion years old, according to University of Oxford astronomer Matthew Hopkins – who is discussing his findings at the Royal Astronomical Society's National Astronomy Meeting 2025 in Durham – and may be the most remarkable interstellar visitor yet.

The Milky Way could have many more satellite galaxies than scientists have previously been able to predict or observe, according to new research.

Rivers are Earth’s arteries. Water, sediment and nutrients self-organize into diverse, dynamic channels as they journey from the mountains to the sea. Some rivers carve out a single pathway, while others divide into multiple interwoven threads. These channel patterns shape flood risks, erosion hazards and ecosystem services for more than 3 billion people who live along river corridors worldwide.

Technicians have installed solar panels onto NASA’s Nancy Grace Roman Space Telescope, one of the final steps in assembling the observatory. Collectively called the Solar Array Sun Shield, these panels will power and shade the observatory, enabling all the mission’s observations and helping keep the instruments cool.

The study leverages state-of-the-art techniques, including TESCAN Integrated Mineral Analyzer (TIMA) mapping and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), to trace mineral zoning and trace element distributions.

The discovery of more than 15,000 kilometres of ancient riverbeds on Mars suggests that the Red Planet may once have been much wetter than previously thought. Researchers looked at fluvial sinuous ridges, also known as inverted channels, across Noachis Terra – a region in Mars' southern highlands. These are believed to have formed when sediment deposited by rivers hardened and was later exposed as the surrounding material eroded. Similar ridges have been found across a range of terrains on Mars. Their presence suggests that flowing water was once widespread in this region of Mars, with precipitation being the most likely source of this water. The new research, led by Adam Losekoot – a PhD student at the Open University, funded by the UK Space Agency – is being presented today at the Royal Astronomical Society's National Astronomy Meeting 2025 in Durham.