---
title: "The Hidden Cost of the Mars Flight: Rat Study Reveals Delayed Risks to Astronauts' Hearts and Immunity"
description: "Researchers at the Medical College of Wisconsin discovered delayed consequences of space radiation and weightlessness in rats: vascular scarring in 83% of animals, a two-third loss of immune NK cells, and persistent genetic mutations increasing the risk of heart attack and leukemia."
date: 2026-10-18T16:16:06.886Z
lang: en
url: https://xab.info/en/posts/hidden-cost-mars-flight-rat-study
tags: [space-research, mars-mission, radiation-exposure, cosmic-radiation, health-risks, nasa, wiscconsin-medical-college, animal-experiments, cardiovascular-disease, immune-system]
author: "Alexander Buran"
publisher: "XAB.info"
---

# The Hidden Cost of the Mars Flight: Rat Study Reveals Delayed Risks to Astronauts' Hearts and Immunity

![A research scientist in a lab examines a laboratory mouse under a microscope against monitors displaying Mars and an astronaut](https://xab.info/media/2026/10/18/skrytaya-cena-poleta-na-mars-issledovanie-na-krysah-vyyavilo-otlozhennye-riski-dlya-serdca-i-immuniteta-astronavtov/skrytaya-cena-poleta-na-mars-issledovanie-na-krysah-vyyavilo-otlozhennye-riski-dlya-serdca-i-immuniteta-astronavtov-1.webp)

## Key Points

- An experiment on rats simulating weightlessness and space radiation using NASA protocols revealed delayed cardiovascular and immune consequences
- At radiation doses expected for a three-year Mars flight, coronary vessel scarring developed in 83% of animals after a year
- The number of NK cells in the spleen decreased by two-thirds; the combination of radiation and weightlessness permanently suppressed bone marrow recovery
- Genetic analysis revealed persistent CHIP mutations, quadrupling the risk of heart attack, stroke, and leukemia
- The authors note limitations: a single radiation dose and participation of only males

Researchers at the Medical College of Wisconsin have concluded that spaceflights may have delayed health consequences that do not appear immediately after exposure to the space environment, but manifest themselves long afterward. This is reported by RBC-Ukraine, citing work published in the professional journal PLOS. Since it is currently impossible to create a full-fledged laboratory outside Earth's protective magnetic field, scientists used special NASA ground protocols to simulate key spaceflight factors — weightlessness and radiation exposure — under controlled conditions.

### How Space Conditions Were Simulated

Middle-aged rats, corresponding to the age category of experienced astronauts, were used for the experiment. Weightlessness was simulated by hindlimb unloading: the animals' hind legs were elevated at a 30-degree angle for 30 days, causing fluid shifts toward the head and removing load from the lower body. Space radiation simulation was conducted at the NASA Space Radiation Laboratory at Brookhaven National Laboratory using the simGCRsim facility, which utilizes heavy silicon and iron ions combined with high-speed protons. Following intense irradiation and a month in the suspended state, the animals were monitored for a year, which is equivalent to approximately 25 human years.

### Cardiovascular Consequences: Scars and Heart Attack Risk

The observation results turned out discouraging for planning future crewed missions to Mars. Scientists recorded that a radiation dose of 1.5 grays caused the development of perivascular fibrosis — the proliferation of connective tissue surrounding coronary vessels and compressing them, significantly increasing the risk of a heart attack. Even at lower doses expected during a three-year Mars mission, scar tissue changes developed in 83 percent of the studied animals a year after irradiation. At the same time, the symptoms themselves appeared not immediately, but after a long time, making them especially dangerous for astronauts, since by the time of detection the pathology may already be irreversible.

### Blow to the Immune System: Loss of NK Cells and Blocked Recovery

Cosmic radiation combined with weightlessness dealt a heavy blow to the experimental animals' immune system. In the rats' spleens, the number of NK cells — so-called natural killers that destroy viruses and tumor cells — decreased by two-thirds. Crucially, while immunity subsequently recovered after weightlessness alone, the addition of radiation permanently suppressed the bone marrow's ability to respond to physiological stress. This means that an astronaut returning from Mars may end up with a chronically suppressed immune system, incapable of adequately fighting infections and oncological processes.

### Genetic Mutations and 'Accelerated Biological Clock'

Genetic analysis of white blood cells conducted 235 days after irradiation revealed persistent mutations associated with clonal hematopoiesis of indeterminate potential (CHIP). On Earth, this process typically accompanies natural aging, when mutated blood cells begin to crowd out healthy ones. Radiation-induced CHIP quadruples the risk of heart attacks and strokes due to inflammation of artery walls, and also increases the likelihood of developing leukemia. Scientists emphasize that radiation effectively 'accelerated the ticking of the cardiovascular system's biological clock,' shifting it into a state characteristic of a significantly older organism.

### Study Limitations and Prospects

The authors of the study honestly point out the existing limitations of the experiment: the animals received radiation in a single dose rather than gradually over several years as would happen in a real flight, and only male subjects participated. Nevertheless, the data obtained form a serious evidentiary base for revising medical protocols for astronaut preparation and developing protective strategies for long interplanetary missions. The results emphasize that the main threat of spaceflight is not acute radiation sickness, but delayed, 'silent' pathological processes that may manifest only years after returning to Earth.

## Fact-Check & Sources

- [Высокая цена полета на Марс: ученые обнаружили скрытую угрозу для астронавтов](https://www.rbc.ua/ukr/news/visoka-tsina-polotu-mars-vcheni-viyavili-1792061133.html) - The primary source contains all key facts: experiment methodology (30-day suspension, simGCRsim at Brookhaven), results (83% scars, loss of 2/3 NK cells, CHIP mutations), limitations (single dose, males only). Publication in PLOS confirmed.

## FAQ

### What experiment was conducted by scientists at the Medical College of Wisconsin?

Middle-aged rats were subjected to simulated spaceflight conditions: 30 days of hindlimb suspension at a 30-degree angle (weightlessness simulation) and irradiation with heavy ions and protons at the NASA Space Radiation Laboratory at Brookhaven National Laboratory. The animals were then monitored for a year.

### What is perivascular fibrosis and why is it dangerous?

It is the proliferation of connective tissue around coronary vessels, which compresses them and significantly increases the risk of myocardial infarction. In the experiment, it developed in 83% of animals even at radiation doses expected for a three-year mission to Mars.

### What impact does space radiation have on the immune system?

The number of NK cells (natural killers) in the spleen decreased by two-thirds. While immunity recovered after weightlessness alone, the addition of radiation permanently suppressed the bone marrow's ability to respond to stress.

### What is CHIP and what role does it play in risks for astronauts?

CHIP (clonal hematopoiesis of indeterminate potential) is a process where mutated blood cells crowd out healthy ones. On Earth, it is associated with aging. Radiation-induced CHIP quadruples the risk of heart attack, stroke, and leukemia.

### What are the limitations of this study?

The authors note that the animals received radiation in a single dose rather than gradually over years, and only male subjects participated. This limits the transferability of the results to real multi-year missions and the female body.