HZE Particle and Neutron Dosages from Cosmic Rays on the Lunar Surface

Abstract

The lunar surface is directly exposed to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) because of the lack of atmosphere and magnetic field on the Moon. These charged particles successively interact with the lunar material and then produce secondary radiations as neutrons and gamma rays. The annual ambient dose equivalent on the lunar surface is estimated about 840 mSv/yr during the quiet period at the solar activity minimum. Particularly, GCR heavy component largely contributes by about 80% to the annual dose equivalents. The ambient dose equivalents of SEPs are also calculated for two transient solar particles events on October 28th in 2003 and January 20th 2005. The SEP protons take the largest contribution of about 90% to the dose, while the heavy components of SEPs do not contribute so much unlike GCRs. The ambient dose equivalent due to the SEP event on 2003 exceeds 2 Sv on the lunar surface. It is clear, however, that an aluminum shield with a thickness of 10 g/cm 2 effectively reduces the dose to 0.1% of total because the solar event has a soft energy spectrum.

Heavy Ion Radiation Exposure Triggered Higher Intestinal Tumor Frequency and Greater β-Catenin Activation than γ Radiation in APCMin/+ Mice

“…However, such radiation exposures were of low linear energy transfer (low-LET) radiation such as γ-ray, which is sparsely ionizing. In outer space galactic cosmic radiation (GCR), unlike solar particle events (SPE), is always present and highly energetic charged (HZE) heavy ions such as 56 Fe, 28 Si, and 16 O contributes significantly to its dose equivalent [5]. While radiation dose during SPE could reach up to 2 Gy behind shielding, long duration space missions are also expected to expose astronauts to considerable levels of cumulative heavy ion radiation doses and are major health concerns [6], [7].…”

Accelerated hematopoietic toxicity by high energy56Fe radiation

“…One of the most biologically important HZE particles is 56 Fe ion. While dose equivalent from proton is only about 5.2%, iron ion contributes almost 22.8% of the galactic cosmic radiation (GCR) dose (Hayatsu et al 2009). Both primary and secondary delta ray tracks from heavy ion radiation is highly ionizing and will cause significant damage to the cells they traverse (Curtis et al 1992, Brooks et al 2001a) with short term as well as long term consequences.…”

Space radiation triggers persistent stress response, increases senescent signaling, and decreases cell migration in mouse intestine

“…Astronauts traveling on long-duration space missions, such as missions to Mars, will be exposed to energetic particle radiation, including protons and heavy ions from solar particle events and galactic cosmic radiation ( 4 , 5 ). While protons are the major component of space radiation, energetic heavy ions such as 56 Fe, 28 Si, and 12 C contribute significantly toward the dose equivalent, and ∼30% of astronauts’ cells are predicted to be hit by heavy ions during a round trip to Mars ( 6 , 7 ). For NASA mission planners, heavy ions are of major concern because they are difficult to block with current shielding measures.…”