Volume 8 Issue 1, January 2024

The current naming conventions for planetary features exacerbate the underrepresentation in space science of women and marginalized groups.

Is the scientific status of astrobiology undermined by the lack of evidence for alien life, the problematic influence of science fiction, or the use of ‘astrobiology’ as a buzzword for attracting funding? Here we defend the emerging discipline.

The search for life elsewhere involves variables across multiple scales in time and space, often nested hierarchically. We suggest that the emergence of artificial intelligence learning systems offers critically important ways to make progress.

The testing of a direct-ascent anti-satellite weapon on 15 November 2021 has prompted renewed efforts in space arms control. A multilateral treaty banning all destructive anti-satellite weapon tests is urgently needed.

Theories predict that core asphericity must be involved in core-collapse supernova explosions; however, the shape of these explosions has not been directly observed. The distribution of the explosive burning ash has now been revealed using nebular spectroscopy, indicating that a collimated structure is common in many stellar explosions.

A low atmospheric carbon abundance can be a ‘habiosignature’ and indicate the presence of substantial surficial liquid water, tectonic activity and/or a biomass in temperate rocky exoplanets. It can potentially be detected by JWST at 4.3 μm in a few tens of transits.

The habitability of a planet is defined at a fixed time. A bigger challenge is to understand how that habitability is sustained over geological timescales, and how the underlying processes compare across different planetary bodies.

On Earth, technological advances required open-air combustion, which needs an oxygen partial pressure of about 18%. This threshold can help guide searches for detectable technospheres on other planets.

If advanced technological extraterrestrial lifeforms are out there, where are they? Thus goes the Fermi paradox. This Perspective reviews various solutions and proposes that they are either not there or are deliberately hiding from us.

Prolonged radio emissions above a sunspot, akin to those auroral emissions previously seen in the polar regions of planets and certain stars, have been detected using the Very Large Array. This detection could potentially provide support for an alternative mechanism for the origin of some stellar radio bursts.

The altered and thermally metamorphosed CY chondrites are shown to be the meteoritic analogue of asteroid Phaethon. This suggests that Phaethon’s activity is driven by gas released from the decomposition of near-surficial material heated at perihelion, whereas the interior is kept relatively unaltered and hydrated.

The Zhurong rover identified polygonal terrain at a depth of 35 m under Utopia Planitia on Mars. This finding suggests that the mid-latitudinal region experienced a cold and wet environment near the freezing point of water around the Hesperian–Amazonian transition, possibly induced by Mars’s high obliquity.

ESA’s Trace Gas Orbiter reveals that the winter night sky on Mars emits visible light between 50 km and 70 km altitude in the polar regions. This nightglow should be observable with simple space camera systems and the naked eyes of future Mars astronauts.

Juno’s close flyby of Ganymede on 7 June 2021 allowed the infrared mapping spectrometer JIRAM to observe the surface at unprecedented spatial resolution. JIRAM’s detailed spectroscopic characterization reveals past extensive aqueous alteration on the moon, possibly together with hydrothermal activity.

Juno’s global infrared mapping of Jupiter’s moon Io determined the distribution as well as the energy output of its volcanoes. Spatial differences emerge, with the equator more active than the polar zones and more heat flow at the north pole than at the south, indicative of an uneven lithosphere.

Chemical disequilibrium is a known biosignature, and it is important to determine the conditions for its remote detection. A thermodynamical model coupled with atmospheric retrieval shows that a disequilibrium can be inferred for a Proterozoic Earth-like exoplanet in reflected light at a high O₂/CH₄ abundance case and signal-to-noise ratio of 50.

Late-phase spectroscopy reveals that explosive nucleosynthesis, occurring in a bipolar collimated configuration, is commonly found for core-collapse supernovae, highlighting the importance of asphericity in shaping these diverse cosmic fireworks.

A rare perfect alignment between two galaxies in the young Universe has been captured by the James Webb Space Telescope. The further (z ≈ 3) galaxy is curved into an Einstein ring due to the bending of space around the nearer (z ≈ 2) galaxy, which is massive and compact—representative of the pristine core of a present-day galaxy.

A lensed quasar at redshift z ≈ 10.3, seen in X-rays, hosts a supermassive black hole of mass similar to that of its host galaxy. The large black-hole mass at a young age, as well as the amount of X-rays it produces, suggest that the black hole formed from the collapse of a huge cloud of gas.

Synchrotron and inverse-Compton emission provide evidence for a reverse-shock origin of the high-energy emission from a gamma-ray burst, GRB 180720B. The polarization of the optical emission originating from the reverse shock suggests a turbulent shock that is amplified by the magnetic field in the relativistic ejecta.