The International Space Station (ISS) maintained an unbroken human presence throughout 2025, marking 25 years since the first crew arrived on November 2, 2000.
Over its lifetime, more than 290 individuals from 26 countries have visited the station, conducting over 4,000 experiments from researchers in more than 110 nations.
In 2025 alone, the station completed over 5,800 orbits while hosting more than 750 investigations. Research addressed life in microgravity, technological innovations for Earth applications, and critical preparations for NASA's Artemis missions to the Moon and beyond.
🚀 Robotic Surgery in Microgravity
NASA evaluated the Robotic Surgery Tech Demo, a miniature robotic system, in microgravity. Researchers used rubber bands to simulate surgical tasks aboard the station.
Results indicated that timing delays from remote Earth operations increased procedure duration but had minimal impact on robotic accuracy. The research suggests potential applications for surgical procedures at lunar bases, on Mars, and in remote areas on Earth.
🧬 Biological and Medical Research
Bone Tissue Regeneration
Roscosmos' Magnetic 3D Bioprinter used magnetic levitation to form calcium phosphate crystal structures in microgravity. These structures exhibited superior organization and capacity for bone tissue regeneration compared to Earth-grown samples, with potential applications for treating skeletal injuries during long-duration missions.
Cancer Treatment Development
Research involving protein crystal growth experiments aboard the ISS contributed to development of a newly FDA-approved injectable medication for several types of early-stage cancers. Microgravity research can produce higher-quality, medically relevant crystals compared to Earth-based laboratories.
3D Printed Medical Implants
Eight medical implants designed for peripheral nerve repair were successfully 3D printed aboard the ISS for preclinical trials on Earth. Printing in microgravity prevents particle settling, resulting in more uniform structures intended to improve blood flow and enable targeted drug delivery in nerve damage cases.
Hematopoietic Stem Cell Expansion
The InSPA-StemCellEX-H2 investigation examines hematopoietic stem cell expansion in microgravity. Returned samples will be analyzed to determine if space-grown stem cells maintain differentiation ability and yield larger quantities for clinical use.
Cardiac Tissue Infection Study
The MVP Cell-09 investigation studies Streptococcus pneumoniae infection of cardiac tissue using stem cell-derived heart tissues infected with pneumonia-causing bacteria. Returned samples will assess cellular responses amplified by microgravity.
Megakaryocyte and Platelet Research
The Megakaryocyte Flying-One (MeF1) investigation studies megakaryocytes and platelets in spaceflight. Samples, including those from astronauts, will inform immune system response in space.
Spaceflight Associated Neuro-ocular Syndrome (SANS)
Researchers will examine whether a daily B vitamin supplement can alleviate SANS symptoms, which cause vision and eye changes in astronauts.
Venous Flow and Blood Clot Study
A study led by Dr. Jason Lytle at NASA's Johnson Space Center will examine whether time in space increases the chance of crew members developing blood clots. Crew members will undergo pre-flight and post-flight MRIs, ultrasound scans, blood draws, and blood pressure checks.
⚙️ Materials Science and Technology
Melanin-Infused Materials
Materials International Space Station Experiment-13 exposed polymers, thermal protection systems, spacesuit components, and radiation-shielding materials to space for six months. Fungal melanin-infused biomaterials exhibited the greatest resistance to radiation damage.
Solid-State Batteries
JAXA demonstrated stable operation of all solid-state lithium ion batteries in space over 434 days, showing stable electrical behavior, no degradation signs, and only 2% capacity loss. These batteries could provide power systems for lunar and Mars missions.
Semiconductor Crystal Production
The SUBSA-InSPA-SSCug investigation produced semimetal-semiconductor composite crystals in microgravity. Returned samples will be evaluated for quality enhancements for electronics.
DNA Nanomaterials Testing
The DNA Nano Therapeutics-3 investigation tests DNA-inspired nanomaterials combined with medicines. Space-assembled materials will be assessed for improved therapeutic performance.
RNA-Based Medicine Testing
The InSPA-Sachi Nanoligomer investigation tests RNA-based medicines on tissue models of brain, heart, liver, and kidney. Microgravity-accelerated aging and disease processes allow observation of drug efficacy.
Bone Scaffold Evaluation
The Green Bone investigation (ESA) evaluates wood-derived scaffold for bone healing. Returned samples will be analyzed to understand bone cell growth on the scaffold in microgravity.
3D Printed Bone Marrow Tissue
The 3D Bone Marrow Analog investigation analyzes 3D-printed bone marrow tissues exposed to vibrations simulating exercise. Returned samples will be measured for mineral formation and genetic changes.
Bioprinted Cartilage Tissue
The InSPA-Auxilium Bioprinter-Cell Printing investigation involves 3D-printed cartilage tissue samples bioprinted in microgravity, aiming for improved cell distribution for joint injury treatment.
Cryogenic Fuel Storage
The Zero Boil-Off Tank Noncondensables (ZBOT-NC) investigation studies gas behavior in cryogenic fuel tanks. Fluid-physics data will validate models for efficient cryogenic storage.
🧑🚀 Human Performance and Health Studies
Post-Mission Piloting Performance
Five astronauts completed simulated aircraft landings before and after long-duration missions. Results indicated degraded performance after return, including higher touchdown speeds and navigational errors, with most pilots recovering on a second attempt the same day.
Manual Piloting Study
A study led by Dr. Scott Wood, a neuroscientist at NASA Johnson Space Center, will assess disorientation during gravitational transitions and evaluate astronauts' piloting and decision-making skills. Select crew members will perform multiple simulated Moon landings before, during, and after their mission, piloting a virtual spacecraft towards the lunar South Pole region. The study includes astronauts on both short-term (up to 30 days) and long-duration (at least 106 days) missions, alongside a control group.
Exercise and Physiological Countermeasures
Astronauts engage in approximately two hours of daily exercise to mitigate bone density loss, muscle weakening, and cardiovascular system changes. Prolonged exposure to microgravity can make readaptation to Earth's gravity challenging. HRP-led studies monitor physiological changes and evaluate solutions including improved exercise regimens, medical monitoring, and nutritional strategies.
Landing Injury Documentation
Upon returning to Earth, select crew members will participate in a study documenting any injuries sustained during landing, such as scrapes or bruises. Data from this research will contribute to improving spacecraft design for enhanced crew protection against landing forces.
⚡ Atmospheric Phenomena
ESA studied electrical phenomena including sprites, blue jets, and elves above severe thunderstorms using space station observations and ground-based radio measurements. Findings correlate blue flash brightness with electrical current, improving models of energy transfer between the upper atmosphere and space.
🌙 Contributions to Artemis Missions
The ISS serves as a platform for developing skills, technologies, and understanding essential for NASA's Artemis campaign.
Orion Spacecraft Systems
Research aboard the ISS helped establish life support and safety systems for the Orion spacecraft, which will transport four astronauts around the Moon during the Artemis II mission. These systems encompass radiation sensing, carbon dioxide removal, portable fire extinguishers, emergency fire masks, the toilet, a heat exchanger, and a backup emergency navigation system.
Artemis II Science Objectives
Several science objectives for Artemis II are rooted in research and methodologies developed on the space station:
- Spaceflight Standard Measures: This experiment tracks psychological and physiological data, expanding to collect astronaut information beyond low Earth orbit to understand human adaptation to deep space.
- Organ-chip Experiments: Small devices modeling tissue and organ responses to space stressors have been used on the ISS. This research will continue in the lunar environment, using cells from Artemis II astronauts to study deep space effects on human health.
- Crew Lunar Observations: Methods from Crew Earth Observations on the ISS inform Crew Lunar Observations for Artemis II, supporting handheld imaging and analysis of geologic features on the lunar far side.
CubeSat Deployments
Small, cost-effective CubeSats, previously deployed from the ISS for technology testing in low Earth orbit, will be deployed during Artemis II for technology demonstrations and studies in high Earth orbit.
📊 Scientific Output and Milestones
Over more than two decades, researchers from over 110 nations have conducted over 4,000 experiments, producing over 5,000 scientific publications cited more than 100,000 times.
On November 2, 2025, the ISS reached a milestone of 25 years of continuous human presence since the first crew arrived on November 2, 2000.