Curiosity did not kill the cat…

So as I’m sure you’ve all heard, NASA’s Curiosity rover successfully landed on the surface of Mars in the early hours of yesterday morning (east coast time). In an earlier post, I relayed the video by NASA of the harrowing entry that Curiosity needed to go through to reach the Martian surface safely and highlighted that the entire elaborate landing procedure was 100% automated since it takes double the time the landing would take to occur for information to be relayed back to Earth. And all the taxings of a mission so complicated, despite all the finesse and delicacy needed to execute such a bold attempt, and despite all the things that could go wrong, the scientists and engineers at NASA succeeded. Honestly, if you watch the 7 Minutes of Terror video, realize that scientists built and programmed a machine that could do that all automatically, millions of miles away from Earth (352 million to be exact) while moving at thousands of miles per hour and have it work flawlessly, and aren’t awed and impressed, then well you should probably check your pulse.

The Mars Science Laboratory’s mission is to investigate the interior of the Gale Crater for signs of microbial life. Top left: A profile of Curiosity’s landing site, Gale Crater. Top Right: A simulation of Curiosity’s proposed mission. Bottom: A map showing the distribution of NASA’s missions to the Martian surface. Credit: BBC News

In addition to being the largest rover we’ve ever sent to another world, twice as long (about 10 feet)  and five times as heavy as NASA’s twin Mars Exploration RoversSpirit and Opportunity, launched in 2003, Curiosity also has new equipment that allows it to gather samples of rocks and soil, process them, and then distribute them to various scientific instruments it carries for analysis; that internal instrument suite includes a gas chromatograph, a mass spectrometer, and a tunable laser spectrometer with combined capabilities to identify a wide range of organic (carbon-containing) compounds and determine the ratios of different isotopes of key elements. There’s clearly a reason why the mission is called the Mars Science Laboratory.

This illustration from NASA shows the size and instrumentation of Curiosity that will help it to investigate the possibility of microbial life on Mars. (A) Six independent wheels allowing the rover to travel over the rocky Martian surface. (B) Equipped with 17 cameras, Curiosity will identify particular targets and then zap them with a  laser to probe their chemistry. (C) If the signal is significant, Curiosity will swing over instruments on its arm for close-up investigation. (D) Samples drilled from rock, or scooped from the soil, can be delivered to two hi-tech analysis labs inside the rover body. (E) The results are sent to Earth through antennas on the rover deck. Return commands tell the rover where it should drive next. Credit: BBC News

According to NASA, Curiosity carries with it “the most advanced payload of scientific gear ever used on Mars’ surface, a payload more than 10 times as massive as those of earlier Mars rovers.” All that gear will be important as Curiosity investigates its main science objective: whether or not there is evidence of microbial life (past or present) in Martian rocks. Although both Spirit and Opportunity listed the search for life as among their scientific goals, neither rover was really equipped to search for microbial life; the twin early generation rovers were more specifically looking for water or the evidence of past water on the Martian surface and then whether that water could sustain life. Curiosity, on the other hand, is specifically equipped to look for microbial life (or evidence of it) in the rocks and soil of the Red Planet. More than just the roving explorer that its forebears were, Curiosity is for all intents and purposes a laboratory on wheels.

This image of Curiosity descending to the Martian surface with its parachute was taken by the High-Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. The rover is descending toward the etched plains just north of the sand dunes that fringe Aeolis Mons. Credit: NASA

And it’s not just the instrumentation that Curiosity is equipped with that make NASA rover 2.0 better than previous generations, but the technology it used to get to the Martian surface is leaps and bounds ahead of how Spirit and Opportunity landed. If you watch this NASA movie that highlights the landing process for the Mars Exploration Rovers (which only had six minutes of terror), you’ll notice that most of the landing procedure seems similar to Curiosity’s. Extremely high-speed entry into the Martian atmosphere, heat shield, parachute, rocket thrusters, etc. Until you get to the last step, when Spirit and Opportunity wer basically dropped onto the Martian surface at nearly 60 mph, surrounded by huge air bags, and allowed to bounce three or four times until they settled. Compared to the fine precision placement of the Curiosity rover earlier this week, the previous rovers’ landings were downright barbaric, like trying to hunt a deer by throwing rocks.

This image, one of the first returned by Curiosity, shows the rover’s shadow on the Martian surface and one of the main targets of its mission, Aeolis Mons, on the distant horizon. Credit: CNN

Rather than violently smashing the $2.6 billion rover into the surface and hoping for the best, this descent involved a sky crane and the world’s largest supersonic parachute, which allowed the spacecraft carrying Curiosity to target the specific landing area that NASA scientists had meticulously chosen. That landing area is roughly 12 km (7.5 miles) from the foot of the Martian peak previously known as Mount Sharp. Aeolis Mons, as it’s now known, is the 18,000-foot (5,500-meter) peak at the center of Gale Crater, previously known as Mount Sharp. The stratified composition of the mountain could give scientists a layer-by-layer look at the history of the planet as Curiosity attempts its two-year mission to determine whether Mars ever had an environment capable of supporting life.

Possibly the biggest piece of the NASA Curiosity puzzle has been the enormous PR campaign that NASA has thrown behind the rover. Not only has the rover and it’s 7 Minute of Terror video been all over the internet, TV news, newspapers, and other media outlets, but NASA has even gone out of its way to get high-level stars in the fold. Last week they released this video (above) of William Shatner, most famously known as Capt. James Tiberius Kirk of Star Trek, narrating a preview of Curiosity’s “Grand Entrance” to Mars. There was also another video featuring narration by Wil Wheaton (Wesley Crusher from Star Trek: The Next Generation).

– Cheers,
Ian Cohen
Manager, UNH Observatory

Modified version of original blog post from The Sky’s the Limit.

Venus: Earth’s Evil Twin…

I have to say, I learn something new about space pretty much every day. A couple of weeks ago I was covering a lecture for an introductory level astronomy class here at UNH. The lecture topic was the formation of the solar system with a highlight on the details of the inner terrestrial planets. So, in preparation for the lecture (the night before), I looked through the textbook: The Cosmic Perspective. And while reading in there about Venus, my mind was blown. What exactly blew my mind? That Venus’s fate could easily have been Earth’s.

Venus, the second planet from the Sun, is the hottest place in the solar system. This radar image from the Magellan spacecraft shows the planet’s surface. Credit: JPL/NASA

Venus is almost the same size as Earth (95% in radius and 81.5% in mass) and made up of pretty much the same stuff. The similarity in size and density between Venus and Earth leads scientists to believe that they share a similar internal structure: a core, mantle, and crust. Both have significant volcanic activity, although Earth has active plate tectonics and we don’t see evidence of that on Venus. The big difference between the two planets comes in the stuff above the planet’s surface: the atmosphere. Earth’s atmosphere is made up primarily of nitrogen (78%) and oxygen (21%), with trace amounts  (~1% or less) of argon, carbon dioxide, water vapor, and other things. On Venus it’s an entirely different story. The Venusian atmosphere is almost entirely made up of carbon dioxide (97%), a very efficient greenhouse gas.

Now you’ve probably heard of greenhouse gases and their role in the greenhouse effect which is playing a role in concerns about global warming. A quick review of how the greenhouse effect works: a greenhouse gas, is a gas (most commonly a hydrocarbon) that allows visible light to pass through it but traps heat from infrared radiation. Okay, so who cares? Well the atmosphere is full of small amounts of naturally occurring greenhouse gases (such as carbon dioxide, methane, and water vapor) which allow the visible light from the Sun to pass through our atmosphere and reach the surface. That’s awesome, because if those gases were opaque to visible light– meaning they did not allow them to pass through– then all the plants on Earth would die and we’d all be sickly pale. It’s this next part that makes greenhouse gases significant. The Earth is warm, astronomically speaking compared to the cold vacuum of space, and emits its own radiation (or light) in the infrared. Back in the mid-19th century, scientists realized that anything that’s warm emits radiation– called blackbody radiation— most of it at wavelengths that we can’t see. The relation between the spectrum of light that an object radiates and its temperature is governed by Planck’s Law. A practical example are night-vision goggles which pick up on the thermal infrared radiation that’s given off by the warmth of a human’s body. Our Sun (10,340º F) is much, much hotter than Earth (~40º F) or a human (~98º F), so it emits a blackbody spectrum which peaks in the visible, whereas humans and the Earth emit mostly in the infrared. It’s the shifting of this peak which gives stars their different colors.

So Earth (and Venus because of its similar size) radiates most of its light in the infrared, which greenhouse gases do not allow to pass through the atmosphere. So instead of that newly radiated heat (IR light) being transmitted out through the atmosphere and into space, it gets trapped and increases the temperature for us on the surface. Now, normally for us on Earth that’s fine because our planet does a great job of regulating the surface temperature through a process known as the carbon dioxide (CO2) cycle. The CO2 cycle helps Earth to self-regulate its temperature. If it’s too hot, the excess carbon dioxide in the atmosphere dissolves in the water in the ocean, then settles and is stored in rocks of the ocean floor. If it’s too cold, then the carbon dioxide which returns to the interior of the planet (via subduction caused by plate tectonics) is released back into the atmosphere by volcanoes. So Earth can do a really good job at keeping track of its own thermostat, which has helped Earth maintain a stable surface temperature even though the temperature of the Sun has changed significantly over time. The problem with the greenhouse effect on Earth is that if we add too many new greenhouse gases (specifically carbon dioxide) that Earth can’t/isn’t ready to handle, then we can mess up the delicate balance that Earth is working so hard to maintain for us.

So what, Venus has more carbon dioxide in its atmosphere, why does that matter to Earth? Well, because it could very easily have happened to us. The only reason that Venus is a horrible, deadly world, the hottest in the solar system, with temperatures over 700º F is because it’s closer to the Sun than Earth is. The average distance of Venus’s from the Sun (called the semi-major axis) is ~72% of that of Earth’s; that means it’s roughly 66,928,200 miles away from the Sun (that’s a mere 26,027,600 miles– or 109 times the distance to the Moon– closer than Earth is). Astronomically speaking, that’s a very small distance. If primordial Earth’s orbit was altered enough to move it that roughly 26 million miles closer to the Sun– by, say an asteroid impact similar to the one that we believe created the Moon— then Earth could have ended up the same as Venus. If Earth were to move that mere 30% closer to the Sun, then the liquid water oceans which we have on Earth that dissolve the excess carbon dioxide, removing it from our atmosphere, would have evaporated. Water vapor is actually one of the best greenhouse gases, so the evaporation of the water vapor into the air combined with the failure to remove carbon dioxide from the atmosphere, would result in a runaway heating effect that the planet would have no way to stop.

So it’s by a very small distance, a distance that’s only 30 times larger than the diameter of the Sun, that Earth escaped being a hellish, fiery deathtrap and became the one oasis of life that we know of in the universe.

– Cheers,
Ian Cohen
Manager, UNH Observatory

Modified version of original blog post from The Sky’s the Limit.