Study suggests increased cancer risk on Mars missions
A new study by researchers at the University of Nevada, Las Vegas (UNLV) suggests the cancer risk for astronauts on a mission to Mars could be higher than expected. The results of the study were published in the May issue of Scientific Reports and show the risk is effectively doubled compared with previous models.
The study builds off of previous research that has suggested prolonged exposure to galactic cosmic radiation can cause cancer, cataracts, circulatory diseases, acute radiation illness, and effects to the central nervous system. While protons are primarily responsible for the absorbed radiation doses in the study, significant contributions were also noted from heavier ions, low energy protons and helium particles, and neutrons.
“Exploring Mars will require missions of 900 days or longer and includes more than one year in deep space where exposures to all energies of galactic cosmic ray heavy ions are unavoidable,” Francis Cucinotta, the lead author of the study explained in a press release by UNLV. “Current levels of radiation shielding would, at best, modestly decrease the exposure risks.”
Cucinotta has a background in studying the effects of the radiation environment of space.
Current radiation risk models assume DNA mutation and damage are the primary cause of cancer, which assumes all cells are impacted by cosmic rays over a short period of time. The new study examined how cancer risk is affected by how healthy, bystander cells are impacted by cells heavily damaged by cosmic rays. The results indicated at least a two-fold increase in cancer rates compared to current risk models.
“Galactic cosmic ray exposure can devastate a cell’s nucleus and cause mutations that can result in cancers,” Cucinotta said. “We learned the damaged cells send signals to the surrounding, unaffected cells and likely modify the tissues’ microenvironments. Those signals seem to inspire the healthy cells to mutate, thereby causing additional tumors or cancers.”
Cucinotta said the study’s findings underline the need for more research into the effects of cosmic ray exposures under Mars mission constraints. Much of the existing body of research has focused on cosmic ray exposure on long duration missions within Earth’s geomagnetic sphere, such as extended flights on the International Space Station.
Cucinotta also said this raises a moral question of sending astronauts to Mars with such a high cancer risk.
“Waving or increasing acceptable risk levels raises serious ethical flags if the true nature of the risks [is] not scientifically understood,” Cucinotta said.
Paul is currently a graduate student in Space and Planetary Sciences at the University of Akransas in Fayetteville. He grew up in the Kansas City area and developed an interest in space at a young age at the start of the twin Mars Exploration Rover missions in 2003. He began his studies in aerospace engineering before switching over to geology at Wichita State University where he earned a Bachelor of Science in 2013. After working as an environmental geologist for a civil engineering firm, he began his graduate studies in 2016 and is actively working towards a PhD that will focus on the surficial processes of Mars. He also participated in a 2-week simluation at The Mars Society's Mars Desert Research Station in 2014 and remains involved in analogue mission studies today. Paul has been interested in science outreach and communication over the years which in the past included maintaining a personal blog on space exploration from high school through his undergraduate career and in recent years he has given talks at schools and other organizations over the topics of geology and space. He is excited to bring his experience as a geologist and scientist to the Spaceflight Insider team writing primarily on space science topics.
Protecting astronauts from the heavy ion component of cosmic radiation and from major solar events only requires about 20 centimeters of water shielding. 30 centimeters of water shielding would expose astronauts to less than 30 Rem per year of cosmic ray exposure during solar minimum conditions. 50 Rem per year is NASA’s limit for astronauts.
The weight penalty resulting from the enhanced water shielding is something that NASA– simply has to accept– in designing its interplanetary architecture.
The obvious solution is to generate a magnetosphere on interplanetary transport spacecraft. That wouldn’t stop high energy cosmic rays but it would deal with the solar radiation. That should bring the risks down to similar levels as long duration LEO missions.
The paper is essentially a computer modeled study, and is somewhat speculative, in my mind.