Early warning system (solar radiation)

Like Earth, Mars has its own Lagrangian points with the Sun. Currently there are no man-made satellites in $L_{1(Mars)}$ or $L_{2(Mars)}$ orbit, but it is conceivable that these islands of gravitational stability may be used to greatly benefit future Mars colonies.

Early warning system for the onset of solar storms

Danger Critical danger of acute solar radiation poisoning. Seek shelter immediately.

Caution Caution recommended. Only travel unprotected for short periods of time.

Safe Minimal solar activity. Preceed with guarded caution. Have a good day :)

A possible simple "flag" system to warn colonists of solar radiation levels

Instruments in the Earth-Sun $L_{1}$ point already provide scientists on Earth with an early warning system to monitor space weather. Probes such as SoHO and ACE receive solar ions approximately an hour before they impact the Earth's atmosphere. This not only provides excellent diagnostic data, but also gives advanced warning to companies and organizations that the Earth is 60 minutes away from experiencing an increase in solar radiation. Emergency procedures can be enacted accordingly, possibly saving delicate satellites and astronauts.

A simple, cost effective probe may be inserted into the Mars-Sun $L_{1}$ point. This probe needn't be as sophisticated as SoHO or ACE, it just needs to monitor the flux of energetic particles travelling toward Mars. Akin to a "flag" system on a patrolled beach (red for "dangerous", no swimming. Green for "safe", water is safe), Mars settlers could have advanced warning of an incoming CME from the Sun. If constantly measured by a particle detector on the probe at the $L_{1}$ point, various stages of danger levels may be used to indicate to settlers unprotected on the surface of what severity of risk they are in. Surface "walkabouts" may be tightly restricted by such a system.

Outstanding design issues

The Mars $L_{1}$ time lag problem?

The distance between Earth's $L_{1}$ point (with the probes measuring solar particles) and the planet is approximately 1.5 million km. This provides information on the solar wind particles approximately 1 hour before they are received on Earth. Mars is a less massive planet than the Earth, therefore, Mars' $L_{1}$ point will be closer to the planet than the Earth's.

Reaching a logical conclusion, assuming solar particles are travelling at the same velocity in near-Mars orbit as with near-Earth orbit, a Mars early warning system of the design outlined above will be less effective than the terrestrial version. So, how much time will the Mars early warning system provide to colonists from detection (at $L_{1}$) to impact (at Mars' surface)?

Using the equation from Lagrangian point calculations:

$r\approx R{\sqrt[{3}]{\frac {M_{M}}{3M_{S}}}}$

where $r$ is the distance of $L_{1}$ from Mars, $R$ is the distance between the bodies and $M_{M}$ and $M_{S}$ are the masses of Mars and the Sun respectively.

Using R = 2.28 × 10¹¹ meters, M_M = 6.4191×10²³ kg and M_S = 1.98892×10³⁰ kg, we arrive at a value of:

$r\approx 1.08\times 10^{9}$ meters or 1.08 million km, 72% of the distance of Earth's 1.5 million km.

Now, keeping the assumption that it will approximately take solar ions 60 minutes to travel 1.5 million km (from Earth's $L_{1}$ point to Earth), the time from $L_{1}$ to Mars' surface = 60 × 72% = 43.2 minutes.

Although 43 minutes is less than the warning time Earth-based solar wind probes are able to provide, this is not a great reduction in lag time, and would still greatly benefit the humans unprotected from solar radiation.