Space exploration was born within a context of acute competition between two superpowers and their allies: the cold war. As such, it was equal parts scientific advancement, technical progress and propaganda tool. Winning the ‘space race’ was a main driver of various milestones, from the early Soviet successes to the American Moon landing to the rush in getting spacecraft to Mars and Venus. It has been argued that this state of global competition actually benefited science and space, which were exceptionally well resourced in terms of workforce and money: NASA received more than 1% of the total federal budget for 12 consecutive years (1962–1974) with spikes of more than 4%. For comparison, NASA received just 0.48% in 2020. Estimates for the Soviet budget cover a similar range.

Despite this tense environment, cooperation in space endeavours and astronomy was never too far away. Already in 1958 the creation of the Committee on Space Research (COSPAR) and of the United Nations Office for Outer Space Affairs (UNOOSA) kept the communication between the two superpowers open in both science and diplomacy, and personal links among researchers developed through private contacts. So, when the space race stopped being a priority, the proponents of peaceful collaboration were ready to take the lead. The symbol of this new era was the Apollo–Soyuz mission, which saw an American astronaut and a Soviet cosmonaut docking two spacecraft together and shaking hands in space in 1975. Few things embody this spirit of cooperation like the International Space Station (ISS): composed mainly of American or Russian modules but also including contributions from Japan and Europe, and visited by people from 19 different countries, it literally cannot function unless the US and Russia work together.

Nowadays international cooperation pervades all corners of astronomy, not just space exploration. International participation on payload, logistics and operations is the norm for planetary missions and space telescopes, as well as several large astronomical facilities on the ground. On a more personal level, contacts among scientists are pervasive and persistent, linking together even those communities divided by government embargoes, for instance between the US and China. We got used to an environment of permanent collaboration in astronomy, where international projects would continue and researchers would gather together regardless of political oscillations.

This rosy-looking state of things came to an abrupt halt at the end of February 2022, with the start of the Russian invasion of Ukraine. Many nations, particularly in Europe, have imposed strict sanctions on Russia with unprecedented swiftness. Usually, science is largely exempted by sanctions, at least directly (although it can be severely impacted at an indirect level). Not this time: very quickly a number of initiatives specifically targeted research, with institutes or countries freezing scientific partnerships, suspending the Russian and Belarusian members from institutions and, hitting where it hurts, removing Russia from research and innovation funding opportunities, such as the Horizon Europe programme. Various conferences planned in Russia were cancelled or relocated, and the flight ban between Russia and many other countries will block the participation of Russian scientists in meetings abroad at a moment where in-person meetings are starting again after two years of pandemic.

Astronomy and space have not been spared, both from the purely scientific side and from the more logistic and technological one. It’s difficult to keep track of the growing list of delayed, suspended or cancelled projects. Nothing has attracted attention like the ISS: if extreme scenarios like the uncontrolled fall of the station to Earth or the stranding of astronauts in space remain confined to inflammatory tweets, questions of its lifespan resurface and the ageing station could shut down way before the planned end-date of 2031. The freezing of cooperation between the Max Planck Society and Russia has put the German X-ray telescope eROSITA on board the Russian SRG spacecraft into safe mode for the time being.

One of the most high-profile victims is probably the Rosalind Franklin rover. This ESA–Roscosmos collaboration, part of the ExoMars mission, was planned to launch in September 2022 from the Russian cosmodrome of Baikonur on a Russian Proton rocket and should have landed a few months later on Mars using a Russian lander mechanism. It is highly unlikely that the launch will happen as planned, as with any other launch from Baikonur — either scientific or commercial — involving the countries that have introduced sanctions against Russia. The video of the covering of the national flags from a rocket at Baikonur that was supposed to take a payload of OneWeb satellites into space is one of the most powerfully symbolic images of this new reality. In a tit-for-tat escalation, Roscosmos withdrew its specialists from the European spaceport of Kourou, and the suspension of operations with Russian rockets there put several launches, including the dark Universe telescope Euclid, planned for 2023, at risk. The fruitful and long-standing cooperation between Roscosmos and ESA and other European space agencies is in tatters and it is hard to imagine a return to the status quo. We are already seeing long-term strategy changes: ESA has declared that it will rely more on its Vega and Ariane rockets, and Russia is eyeing a tighter collaboration with China.

Researchers are currently facing a difficult decision. Even many of those institutions that cut or froze bilateral contacts with Russian/Belarusian institutions encouraged their own researchers to keep personal contacts alive, also considering that many Russian and Belarusian academics have expressed concern and condemned the war. How to proceed from here is a very personal choice, and every approach has its own justification. We, as editors, respect all these choices in this extremely difficult moment and we stand by the stance expressed by a recent Nature editorial, condemning the attack on Ukraine without blocking scientific communication through a boycott of Russian research. As our space race history teaches us, maintaining some bridges in divided times may help rekindle cooperation when happier times will come, for everyone’s benefit.