I don't know the atmospheric pressure of your world, so I'll assume that it is like Earth's: 101.325 kPa.
Atmosphere: 101.325 kPa
- 35% oxygen.
- 61% argon.
- 1.07% carbon dioxide.
- 0.93% arsenic.
- 2% other trace elements.
First
Arsenic is:
- Deadly poison. Here you can read about the symptoms and more information.
- Impossible for it to be a gas in your current atmosphere (you need to change the pressure and temperature of the atmosphere a lot to 615°C).
Second
To calculate the partial pressure of gases I need know the molecular mass of other trace elements
, because I don't know them I will replace them with N2 (a really common gas).
Partial Pressure
$$ \left|
\begin{array}{cc|ccc|c|c}
\hline
\text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (kPa)}&0.66 \text{ g}\\
\hline
\text{O}_{2}&\text{35%}&32&1.09&\text{40.08%}&40.61&26.8\\
\text{Ar}&\text{61%}&39.95&1.53&\text{55.96%}&56.7&37.42\\
\text{CO}_{2}&\text{1.07%}&44.01&0.02&\text{0.89%}&0.9&0.6\\
\text{As}&\text{0.93%}&74.92&0.01&\text{0.45%}&0.46&0.3\\
\text{N}_{2}&\text{2%}&28.01&0.07&\text{0.45%}&2.65&1.75\\
\hline
\text{Total}&\text{100%}&218.891&2.73&\text{100%}&101.325&66.8745\\
\hline
\end{array}
\right| $$
- High oxygen value: Humans need around 21 kPa of oxygen to "work" properly, you have the double, your people would suffer hyperoxia. Also when oxygen is above 50 kPa it becomes toxic, luckily your O2 isn't toxic but would be annoying for your population.
- Argon Asphyxia: Although argon is non-toxic, it is 38% denser than air and therefore considered a dangerous asphyxiant gas in closed areas. It is difficult to detect because it is colorless, odorless, and tasteless.
- Argon narcopsia: I don't know much about it but I think it can cause narcopsia like nitrogen (56.17 kPa of argon is very much, maybe it could produce some dizziness). Also, I am not sure but Xenon weakens the blood-barrier brain and this increase the probability of infections in the brain, argon and xenon are inert gases, anaesthesic and narcotic, maybe argon also weakens the barrier.
- CO2 slightly above the normal: maximum amount of CO2 in air can be 1% without visible problems, at 1.5% you would die in a month, you have 1.07%, maybe it could take years to kill you or your body will adapt to survive.
- Lethal arsenic: see above.
For more information about gases in the atmosphere you can check this answer (effect of several gas with an emphasis in O2) and this answer (effect of several gas in extreme doses with an emphasis in CO2 intoxication).
Your world has 0.66 g gravity and you don't indicate the pressure of your atmosphere. The information above assumes that the pressure is equal to Earth's but I don't know if it's same pressure or same amount. If it's the second option then its partial pressures will be found in the last column of the table, in that case you won't have hyperoxia, but argon could still be dangerous.
Sorry, but I don't know about your additional question, (I'll compensate for that with a free check of atmospheric stability!.
Calculating if gases will escape!
1) Calculation of the escape velocity:
In physics, escape velocity is the minimum speed needed for an object to escape from the gravitational influence of a massive body.
- Escape Velocity = $\text{v}_\text{e} = \sqrt{\frac{2\times\text{G}\times\text{M}}{\text{r}}} = \sqrt{2\times\text{g}\times\text{r}}$
- Where:
- G is the gravitational constant: ($\text{G} ≈ 6.67 \times 10^{11} \text{ m}^3 \times \text{kg}^{-1} \times \text{s}^{-2} ≈ 0.0000000000667$)
- M is the mass of the body to be escaped (planet) in kg.
- R is the distance from the center of mass of the body to the object in metres.
- g is the gravity in m/s2.
The problem is we don't know the radius of your planet:
Gravity can be calculated:
$${\displaystyle g={\frac {m}{r^{2}}}}$$
Where g is the surface gravity of the planet, in a multiple of the Earth's, m mass, in multiples of the Earth's mass (5.976·10^24 kg) and r its radius, expressed as a multiple of the Earth's (mean) radius (6,371 km).
So, to calculate the radius I can do:
$$r = \sqrt{m \times g}$$
On an exoplanet with 0.284 Earth-mass and a surface gravity of 0.66 g (6.44 m/s^2).
$$r = \sqrt{0.284 \times (0.66)} = \sqrt{0.18744} = 0.43$$
$$0.43 \times 6,371 \text{ km} = 2758.28 \text{ km}$$
So:
$$v_e = \sqrt{2gR} = 5,960 \text{ m/s}$$
2) Now if the RMS (Root-mean-square speed) velocity of any gas in your atmosphere is equal or greater than escape velocity of the planet then that gas will escape rapidly and will be absent.
- $\text{RMS} = \text{v}_{\text{rms}}=\sqrt{\frac{3\times\text{R}\times\text{T}}{\text{M}_{\text{m}}}}$
- Where:
- $\text{Vrms}$ is the root mean square of the speed in meters per second.
- $\text{Mm}$ is the molar mass of the gas in kilograms per mole.
- $\text{R}$ is the molar gas constant. $\text{R} = 8.3144598(48)\text{ J}\times\text{mol}^{-1}\times\text{K}^{-1}$
- $\text{T}$ is the temperature in degrees kelvin (K = °C + 273.15). I'll use 25°C (298.15 K), I think that is the "normal" temperature used in gas calculations where it's specified.
$$ \left|
\begin{array}{c|c|c}
\hline
\text{Gas}&\text{kg/mol}&\text{RMS}\\
\hline
\text{O2}&0.032&482.08 \text{ m/s}\\
\text{Ar}&0.039&431.45 \text{ m/s}\\
\text{CO2}&0.044&411.07 \text{ m/s}\\
\text{As}&0.074&315.06 \text{ m/s}\\
\text{N2}&0.028&515.27 \text{ m/s}\\
\hline
\end{array}
\right| $$
Your atmosphere is stable! (or at least for short-term, I don't know how to calculate the Boltzman distribution for geological ages).