Amendment Notice:
Please note a correction to the submission guidelines. The field “Complete description of the idea” was mistakenly listed as allowing up to 4,000 words. The correct limit is 4,000 characters. We apologise for the confusion and ask applicants to follow the corrected requirement.
1. INTRODUCTION
ESA's Exploration Science: Advancing Knowledge, Inspiring Innovation
The European Space Agency's Exploration Science element, a cornerstone of its Explore2040 strategy, invites scientists, researchers, and innovators to join us in pushing the boundaries of human knowledge and technological capabilities. Our programme uniquely balances exploration-focused science, essential for enabling future human missions beyond Earth, with exploration-enabled science that leverages our capabilities for groundbreaking research across disciplines.
From the microgravity environment of low Earth orbit (LEO) to the dusty plains of Mars, we offer unparalleled opportunities to conduct cutting-edge research. Our comprehensive approach spans multiple destinations - including the International Space Station (ISS), future commercial LEO platforms, the lunar Gateway, the Moon's surface, and Mars - providing a diverse array of research environments and challenges.
Guided by core European values of collaboration, scientific excellence, and responsible exploration, we seek ideas that not only advance our understanding of the universe but also contribute to solving global challenges here on Earth. Exploration Science emphasises open science, international cooperation, and the inspiration of future generations.
Developing countermeasures for long-duration spaceflight, investigating fundamental physics in microgravity, prospecting for lunar resources, or searching for signs of past life on Mars, ESA Exploration Science offers a platform to turn your scientific vision into reality.
A VT was identified in the internal jugular vein (IJV) of an astronaut during a research study of fluid shifts in weightlessness (Auñón-Chancellor et al., 2020). This incidental finding was subsequently confirmed by a clinically guided ultrasound examination with 2-D imaging, colour Doppler, and compression (Marshall-Goebel et al., 2019). While the crewmember was successfully treated with anti-coagulants in orbit and regression of the thrombus was observed over the course of therapy, the thrombus persisted through 90 days of treatment. Anti-coagulation therapy was discontinued four days before landing, and the astronaut was safely returned to Earth without further complications. No thrombus was detected 10 days after landing, and the astronaut was asymptomatic during the subsequent 6 months. Additionally, in a retrospective evaluation of the images from the research study, a partially occlusive thrombus was suspected in a second crewmember, but it was confirmed using standard clinical practices (Marshall-Goebel et al., 2019).
Following this event, medical surveillance for VT was initiated among United States Orbital Segment (USOS) astronauts (Pavela et al., 2022). Current medical assessments required for ISS astronauts include assessment of genetic predisposition to thrombosis and preflight MRI imaging of the head and neck (TWIST sequence with gadolinium contrast), as well as bilateral duplex ultrasound of the extracranial IJVs with breathing and compression maneuvers performed before and during spaceflight. Since the initial case was asymptomatic, there is a concern that there may have been other cases that were overlooked or undetected given the relatively large proportion of astronauts in whom characteristics of impaired IJV flow or stasis has been observed (Marshall-Goebel et al., 2019, Pavela et al., 2022).
Previously, IJV thrombosis was not a recognised concern for crew health during weightlessness, owing to its low terrestrial prevalence (Limper et al., 2021). Hence, several peer-reviewed publications (Kim et al., 2021, Harris et al., 2022a, Harris et al., 2022b, Harris et al., 2023, Levasseur et al., 2024) have aimed to describe factors that might contribute to VT during spaceflight. Summaries of the current state of knowledge and plans for future work are documented in NASA’s Office of the Chief Medicine Office Technical Brief (Annex 1), ESA’s Operations-Focused Uncommon VT Strategic Roadmap (Annex 2), and ESA's HRE-HM (MedOps) Priorities for Exploration Enabling Science document (Annex 3). More recently, NASA and ESA have partnered to initiate a comprehensive pre- and inflight study of cerebral venous outflow, anatomical variation, and biomarkers of hemostasis to be completed before the retirement of the ISS.
Thus far, VT has only been reported in an astronaut participating in a long-duration mission to the ISS, but other future research platforms might include commercial vehicles for orbital and suborbital spaceflight. To date, there have been no reports of VT or IJV flow impairments/stasis in strict head-down tilt bed rest (HDTBR) (Laurie et al., 2025), but stasis has been observed in a small number of study participants during acute exposures (~20-25 seconds) to weightlessness (Marshall-Goebel et al., 2024) and partial gravity during parabolic flight (Lytle et al., 2025). Given that medical capabilities during exploration missions to the Moon and Mars may be limited, the identification of prophylactic countermeasures to mitigate the risk of VT and interventions that can be used to manage thrombosis cases are of great importance to crew health and mission success. Several mechanical countermeasures that might mitigate cerebral outflow abnormalities during weightlessness have been evaluated in spaceflight (Hamilton et al., 2012, Marshall-Goebel et al., 2019) and spaceflight analogs (Marshall-Goebel et al., 2021, Laurie et al., 2025), such as lower body negative pressure (LBNP), venous occlusion thigh cuffs (VTC), and an impedance threshold devices (ITD). VTCs are currently used by astronauts during the early phases of a mission to manage symptoms of the headward fluid shift (Hamilton et al., 2012) and are being assessed as a countermeasure for Spaceflight-Associated Neuro-ocular Syndrome (SANS) and evaluated for their potential influence on IJV flow.
NASA and ESA are seeking recommendations for enhanced or novel approaches to reduce the risk of, surveil, and/or treat VT during spaceflight and exploration. These recommendations should consider limitations of habitable volume in space vehicles and habitats and constraints on mass of hardware for launching into orbit (Abercromby et al., 2025).
The information obtained will be used by NASA and ESA for planning and acquisition strategy development. NASA and ESA will use the information obtained through this RFI on a non-attribution basis. Providing data and information that is limited or restricted for use by NASA and ESA for that purpose would be of very little value, and such restricted/limited data/information is not solicited. No information or questions received will be posted to any website or public access location. NASA and ESA may respond to individual responses.
Appropriate responses to this RFI should address:
- Recommendations for development and validation of approach(es) to surveil, reduce the risk of, and/or treat VT during spaceflight and exploration missions, including rationale and methodology. Approaches might include technologies currently available and those in development as well as applications in LEO and during missions to the Moon and Mars where capabilities may be further constrained by vehicle stowage limitations, power allocations, and real-time communication delays with increasing need for Earth-independent operations.
- If applicable, recommendations for future spaceflight and spaceflight analog research relevant to VT during spaceflight and exploration missions. Relevant applications might include short- and long-duration missions in LEO, missions beyond LEO, and habitation in partial gravity environments. Analogs might include relevant patient populations, parabolic flight, and suborbital flight.
