LIRA
Laboratory for Instrumentation and Research in Astrophysics

LIRA, a pioneer in astrophysics and instrumentation, pushes back the frontiers of knowledge

LENS: LIRA – Weekly Highlight

Deep-learning maps of fresh crater rays on Mercury

25 May 2026

On Mercury, some young impact craters are surrounded by bright, filamentary “rays”: ejecta made of relatively immature material excavated by the primary impact and by secondary impacts. Over time, space weathering (micrometeoroid bombardment and solar-wind irradiation) darkens these deposits and the rays fade, making them a useful indicator of geologically young surfaces (hundreds of Myr). In his PhD work at LIRA, Michele Lissoni developed a deep-learning approach that combines a connection model (is a tile linked to a crater by a ray?) with a segmentation model (where is the ejecta?), trained on the global MDIS Enhanced Color mosaic at 665 m/pixel. The resulting global product overlays ejecta masks from many craters—each in a different color—opening the door to systematic studies of ray geometry, spectral properties, crater ages, and impact dynamics.

Credits: MESSENGER/MDIS/M. Lissoni
COLLOQIUM Monday 1 June 2026 11:00
Colloquia du LIRA
Elodie Choquet (LAM, Marseille) : ESCAPE project: investigating observing and image processing methods for exoplanet direct imaging with future space...
SEMINAR Monday 1 June 2026 14:00
Séminaires du pôle Étoiles et Galaxies
Mar Carretero-Castrillo : Massive runaway stars in the Milky Way: new insights from Gaia and multiwavelength studies
SEMINAR Monday 1 June 2026 16:00
Théminaires Planétologie
David Boulesteix : La chimie radiative est l’ange caché et la chimie de l’eau est le démon caché

Presentation

LIRA, a CNRS joint research unit at Paris Observatory, is a laboratory of excellence in astrophysics and instrumentation. It studies astrophysical objects, from the Solar System to our Galaxy and beyond, through five thematic areas. Through international collaboration and instrumental innovation, it pushes back the frontiers of science and contributes to the training and dissemination of knowledge.

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Our projects

MIRS on the JAXA MMX mission

The Martian Moons eXploration (MMX) mission of JAXA (Japan Aerospace Exploration Agency) is the first sample-return mission from the Phobos satellite. It also includes an exploration of the Martian system. The mission’s primary objective is to decipher the origin of Martian moons, which will provide important information on planet formation and the conditions for the emergence of water on Earth-like planets.

The MIRS (MMX InfraRed Spectrometer) instrument, developed under the leadership of LESIA (now LIRA), is an imaging spectrometer that will characterize the composition of the Martian system and help select candidate sites for sample collection.

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GRAVITY+

The GRAVITY instrument, installed on the European Southern Observatory’s Very Large Telescope Interferometer (VLTI/ESO), has produced spectacular and transformative results on the supermassive black hole at the centre of the Milky Way, the active nuclei of other galaxies, proto-planetary disks around young stars and exoplanets. GRAVITY+ aims to modernise both VLTI and GRAVITY to make them ≈ 100 times more sensitive, while increasing sky coverage by a factor of ≈ 100, and contrast in the vicinity of bright objects by a factor of ≈ 10. These gains will benefit all the VLTI’s current and future instruments for the next 20 years, and will perpetuate it as a unique infrastructure in the world.

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Contacts

Contacts

Postal address
Observatoire de Paris
5, place Jules Janssen
92195 Meudon

Phone
01 45 07 77 01

Mail
contact.lira@obspm.fr

Meudon site

LIRA
Observatoire de Paris
5, place Jules Janssen
92195 MEUDON Cedex

How to get to Meudon

Paris site

LIRA
Observatoire de Paris
77, Avenue Denfert-Rochereau
75014 Paris

How to get to Paris

Cergy site

LIRA - Site de Neuville II
UFR Sciences et Techniques - Département de physique
5, mail Gay Lussac
95000 Neuville-sur-Oise

How to get to Cergy