The authors thank the referee for this comment that demonstrates that the authors need to clarify. However, to the authors it is not clear which potentially inactivating components of the plasma are not specified, as radicals and radiation are mentioned and the temperature is kept below 80°C to prevent inactivation effects due to heating. As the samples are placed in an ICP discharge, ions towards the samples are only accelerated by several tenth of eV. Thus, sputtering of the sample due to ion bombardment can be neglected. Low-pressure plasmas dissociate molecular gases up to several percent. Thus, the authors wanted to emphasize, that the atomic oxygen density and therewith the atomic oxygen flux to the samples is in the order of a few percent of the overall gas flux. Quantitative and even qualitative analysis of atomic oxygen densities by optical emission spectroscopy is not an easy task as several parameters like gas temperature, electron density and electron temperature are necessary. This is even more challenging in pulsed mode, as the plasma does not achieve a steady state due to switching it on and off to prevent intensive heating of the plasma. Determination of the gas densities and plasma parameters is currently addressed in extensive analysis of plasmas with different gas compositions but not finished and published yet. Nevertheless, the authors’ state, that a relevant amount of atomic oxygen species is produced in the low pressure argon-oxygen plasma as the minimum energy for dissociation of molecular oxygen is around 5 eV. The ionization energy for argon is 16 eV and 13 eV for molecular oxygen. Thus, sufficient electrons with enough energy to dissociate molecular oxygen will be present in the plasma for dissociation up to a few percent. In the authors’ view, estimating the mean free path of the atomic oxygen in the plasma is not necessary, as recombination of radicals in low pressure plasmas in the regime of a few Pascal takes place at the surfaces. Thus, any radical formed will be lost at the walls and not on its way to a surface. Estimating the mean free path of the radical in the Mars Analog Soil can only be performed on an arbitrary basis as the sticking and recombination coefficients of atomic oxygen are not known for the Mars Analog Soil. Thus, any calculation of the mean free path of the radical is based on estimated data and could only be verified by experiments. To address the reviewer’s comments, subsection 2.3 has been modified as follows: Only JSC Mars-1A analog soil was used in the second trial. In this case, an argon-oxygen mixture (100:5 sccm) was used as it produces reactive oxygen species due to dissociation of molecular oxygen in the plasma. Since radiation-based sterilization is faster than sterilization due to oxidation, the treatment time was increased. As this leads to heating of the sample above 80 °C in the continuous plasma, we used a pulsed mode, switching the plasma on and off at a frequency of 1 kHz and a duty cycle of 10 %. To account for this fact, the treatment time was increased to 45 min, yielding a plasma exposure time of 4.5 min. Furthermore, the power was increased to 1500 W, yielding a mean power of 150 W, as it is only applied 10 % of the time. The plasma conditions are not matched to each other as the main objective was to observe to what degree the cells of D. radiodurans were affected by radiation or reactive species and not which component is more efficient. Thus, sputtering of the sample due to ion bombardment can be neglected as possible inactivation mechanism.
Minor comments Lines 31-32: Bacillus subtilis and B.pumilus should be written in italic.