Look for the Mars triangle low in the southwest starting an hour after sunset. Created with Stellarium

If you could travel there at the speed of light that is. Curiosity Rover has been on its way since last November and will finally arrive late this weekend.

Mars is nearly 153 million miles from Earth today. You’ll find the planet low in the southwestern sky beginning about an hour after sunset. It’s joined by Spica and Saturn in a nifty triangle, and all three are within a few tenths of a magnitude of each other. For the record, Saturn is brightest at magnitude 0.7, Spica 0.9 and Mars 1.1. Can you distinguish these slight differences in brightness?

I just think it’s cool to be able to see the real planet, the place where our attention will be focused Sunday night, as we await confirmation of the Mars mission touchdown. The real Mars, that spark of orange-pink in the fading sky, will soon be host to another emissary from Earth. Let’s hope the planet welcomes our curious robot with open arms. No crash landings please!

A plutonium pellet glowing under its own energy. Plutonium decays into uranium as it releases heat than can be converted into electricity. Credit: Dept. of Energy

The Curiosity rover bristles with instruments for exploring everything from Martian weather to taking pictures to determining the chemical composition of the soil.

Unlike all earlier rovers, Curiosity won’t be dependent on sunlight for its energy. Instead it uses a radioisotope thermoelectric generator (RTG) powered by 32 marshmallow-sized plutonium-238 pellets weighing all of 11 lbs.

Lots of instruments and Curiosity’s expected 2-year lifetime requires plenty of energy. Plutonium-238 is ideal for the job. The rover, also called the Mars Science Laboratory, measures 9.8 feet across. Credit: NASA

The heat released by plutonium as it decays into uranium is converted into electricity to power the rover day and night through all seasons. Because the other rovers were powered by solar energy, they were laid up during the Martian winter when the sun was too low to provide the energy to run it around and perform experiments. Dust also occasionally covered their solar panels, causing the power flow to drop. NASA mission controllers would have to temporarily scale back the rovers’ progress in response until a lucky dust devil would vacuum the panels clean again.

The rover landing we’re putting the ground Sunday is like one of those self-contained food trucks you see on city streets nowadays only it does science instead of food service. Let’s briefly check out the purpose of each instrument, so you’ll have a handle on terminology as the story of discovery unfolds.

* Mast cam – Contains two color cameras for narrow-angle and medium-angle imaging. Can also shoot video up to 10 frames per second. There are also 8 “Hazcams” or Hazard-Avoidance cameras at the front and back of the rover and 4 Navigation cameras on the mast. They take fisheye photos in stereo of the near terrain.

* Mare descent imager (MARDI) – This camera will take images of the ground during the rover’s descent at the rate of 5 frames per second starting at 2.3 miles all the way down to 16 feet. Total shooting time: 2 minutes

* Mars Hand Lens Imager (MAHLI) – Camera mounted on a robotic arm to snap microscopic images of Mars rocks and soil.

* Radiation Assessment Detector (RAD) – Instrument to measure the radiation inside the rover en route to Mars and while on the surface. The data will help determine how much shielding a manned expedition to Mars would require.

* Alpha Particle X-Ray Spectrometer (APXS) – Blasts soil samples with alpha particles and measures the X-rays emitted to determine what elements they’re made of.

* Rover environmental monitoring station (REMS) – A weather station to measure pressure, humidity, wind speed and air temperature.

* ChemCam – Will shoot a infrared (invisible) laser at a rock or soil sample up to 23 feet away, vaporize it and analyze the resulting puff  with a spectrograph to determine the soil composition.

* Dynamic albedo of neutrons (DAN) – Instrument to bombard the soil with neutrons (subatomic particles) to detect hydrogen from possible water or ice at or just beneath the surface.

* Sample Analysis at Mars (SAM) – Located inside the rover, these instruments will analyze organic compounds and gases from soil sample and the atmosphere.

* Chemistry and Mineralogy (ChemMin) - Using the Sample Acquisition and Processing unit, the rover will drill into rocks, collect the fine powder and then deliver it to ChemMin. As a beam of X-rays irradiates the soil, individual minerals diffract or scatter the X-rays in characteristic patterns. Using a spectrograph to measure those patterns, scientists will learn the composition of the minerals.

The whole works is a Chemistry 101 lab on wheels with more sophisticated Bunsen burners.