Space Sunday: China, Mars and the Drake Equation revisited

A colour close-up captured by China’s Zhurong rover via its high-resolution cameras as they look over the rear deck, showing the main communications relay and one of the unfolded solar arrays. This image was captured before the rover deployed from its lander. Credit: CNSA

China’s Zhurong rover has commenced operations on the surface of Mars. The rover, which is slightly larger and heavier than NASA’s MER rovers Spirit and Curiosity, arrived on the surface of the planet on May 16th atop its lander vehicle (see: Space Sunday: China on Mars, JWST and a space tourist).

Since that time, the rover has been put through its first battery charging cycle after unfolding its solar panels, and then entered an initial telemetry-based check-out and commissioning phase that saw some of its core systems powered-up in readiness to commence operations, with similar checks being carried out on the lander.

An infographic on China’s Zhurong rover via AFP, with original material via CNSA and Chinese state media

This meant that it was not until May 19th that the China National Space Administration (CNSA) released the first images taken by the rover’s camera systems.

The first images to be released were those captured by Zhurong’s hazard avoidance cameras, which – and like their American counterparts – operate primarily in black and white. In particular, these images showed that the lander vehicle had successfully deployed the ramp Zhurong needed to descend onto the planet’s surface from the back of the lander.

The black-and-white images were followed by colour pictures captured by both the rover’s hazcam system and its high-resolution imaging system which is, again like US designs (and the upcoming EuroMars rover, Rosalind Franklin, mounted on a mast located on the rover’s forward section and capable of taken images of all of the rover’s surroundings.

China’s Zhurong (l) and America’s Perseverance (r) in a comparison image by CNSA

China has been fairly close-lipped about the lander and rover – although the entire Tiawen-1 mission is seen as an “international” mission by Chinese authorities -,  only releasing images via social media, etc., after the fact, with little or no fanfare beforehand. This meant it was Twitter snoops who first spotted the rover had actually deployed from this lander vehicle some time in the early hours of Saturday, May 22nd, UTC.

Andrew Jones was one of the first to spot CNSA images that showed the rover had rolled off the lander. However, CNSA quickly followed-up with more images captured by the rover, some of which were colour, and others were put together to form a “video” of the deployment process.

Andrew Jones was one of the first to spot China had announced Zhurong had driven off of its lander.

Now it is on the surface of Mars, Zhurong is expected to operate for a primary mission period of 90 sols (93 days) – which is likely to be extended if the rover completes that mission successfully. It will explore the area around its lander, using both it and the Tianwen-1 orbiter as communications relays, while carrying out research into the Martian weather and climate, and surface and sub-surface conditions.

The return of the first images from the rover sparked an appeal to the US Congress from NASA’s new Administrator, Bill Nelsen, who asked for a boost to the agency’s funding so that it might better manage deep space research and the planned return to the Moon in the face of the growing competition from China.

A colour picture from Zhurong’s hazcams as it roles down the ramp from the lander on May 22nd. Credit: CNSA

It has not all been smiles and roses for China, however. As  I previously reported, the country can in for international criticism for failing to handle the uncontrolled return to Earth of the 23-tonne core stage of the long March 5B core stage used to lift the Tianhe primary module of the country’s new Tiangong space station. Following up from that mission, China had planned to launch its first mission to Tianhe on May 19th.

This was to be the Tianzhou-2 automated resupply vehicle. A fully automated, 13-tonne vehicle, Tianzhou-2 was supposed to make an automatic rendezvous  and docking with Tinahe in advanced of the first crewed mission to the fledgling space station, which is due to occur in June, 2021; however, the launch was scrubbed as a result of “technical issues”. Initially re-scheduled for lift-off on Thursday, May 20th, the launch was again postponed, and has now been pushed back until Friday, May 29th.

A Chinese Long March 7 rocket carrying the Tianzhou-2 cargo ship rolls out to a launch pad at the country’s Wenchang Satellite Launch Centre on Hainan Island. Credit: CASC.

When Tianzhou-2 does eventually lift-off atop its Long March 7 booster, it will be carrying 6.5 tonnes of equipment and supplies for the first crew to visit Tianhe, and consumables for the station itself, and will remain docked through the 3-month period of the Shenzhou-12 crewed mission. During the crew’s visit, Tianzhou-2  will perform a set of automated undocking, free flight and rendezvous / docking manoeuvres as rehearsals in readiness for when the station’s science modules are launched.

Tianzhou-2 will depart Tianhe ahead of the Shenzhua-12 crew. The station will then be visited by a further automated res-supply vehicle and the Shenzhou-13 crew, over late 2021 / early 2022, for the Chinese are calling the “Critical Technology Validation Phase” of the station’s commissioning, verifying it is ready for the launch of the two science modules. These will take place in 2022, paving the way for full operations to commence from 2023.

ExoMars Parachute Passes Critical Test, and Curiosity from Space

Going back to Mars for a moment longer, ESA’s much-delayed European / Russian ExoMars rover/lander mission (now due to launch in 2022), passed a further critical test in May, when its extensively redesigned supersonic parachute and release system passed a series of ground-based tests at facilities operated by NASA’s Jet Propulsion laboratory.

The rover – the Rosalind Franklin – and its lander are due to use two parachute during their descent to the surface of Mars in mid-2023. The first is a 15-metre diameter ‘chute designed to be deployed when the vehicles are travelling through the Martian atmosphere at supersonic speeds.  It is intended slow them to a point where a 35-metre diameter sub-sonic parachute can be deployed to bring them down towards the Martian surface.

A model of the ExoMars rover, Rosalind Franklin, in the ROCC Mars Yard. Credit: ESA

Issues with the deployment of the supersonic parachute had plagued the mission for several years, and following the postponement of a planned 2020 launch due to other issues, the decision was taken to have both contractors developing the high-altitude parachute system to re-design both the parachute and its deployment mechanism. During the JPL tests, both ‘chute designed worked perfectly, clearing the way for them to move to high-altitude drop tests, which are currently due to take place in June.

Should these be successful, one of the parachute systems will be selected for the mission and go forward for integration with the rest of the landing systems in readiness for ExoMars to be launched in September 2022.

Meanwhile, although attention has been on the Chinese rover and NASA’s Perseverance and Ingenuity helicopter, the Mars Science Laboratory Curiosity has continued to explore Gale Crater. On May 21st, NASA released an image captured by the Mars Reconnaissance Orbiter (MRO) as it passed over Gale Crater at an altitude of 269.4 km on May 18th, 2021.

Almost smack in the centre of the image is Curiosity as it ascends “Mont Mercou”, a transitional region on the slopes of “Mount Sharp” (Aeolis Mons), the 5 km high mound in the middle of the crater. The image was captured on April 18th using its High Resolution Imaging Science Experiment (HiRISE) instrument, which can resolve features as small as a coffee table on the Martian surface. So the car-sized Curiosity is plainly visible.

The HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter captured this photo of the Curiosity rover ascending Mont Mercou on April 18, 2021. Credit: NASA/JPL

The “Mont Mercou” area is of particular interest to scientists as it marks a point where the minerals within the rocks of “Mount Sharp” shift from being clay heavy, indicating the level below which the crater was a lot wetter (and possibly underwater in the distant pass), to become more salty sulphate in nature, indicating parts of “Mount Sharp”  that have been exposed to the environment and free from liquid water for much longer. Investigation of this area may well reveal further Martian secrets.

Redefining the Drake Equation

First postulated by Frank Drake in 1961, the Drake Equation was intended as a means by which scientists could encapsulate the challenges of trying to engaging in a Search for Extra-Terrestrial Intelligence (SETI).

Specifically formulated by Drake to stimulate discussions on the subject at the first ever SETI conference, organised by Drake and the legendary Carl Sagan. It  is stated as:

The equations is stated as:

N = R* x fp x ne x fl x fi x fc x L

Where:

  • N is the number of civilizations in our galaxy we could communicate with
  • R* is the average rate of star formation in our galaxy
  • fp is the fraction of stars with planetary systems
  • ne is the number of planets that can support life
  • fl is the number of those planets that will develop life
  • fi is the number of those planets that will develop intelligent life
  • fc is the number of civilizations that might develop transmission technologies
  • L is the amount of time that these civilizations would have to transmit their signals into space.

It all sounds very scientific, but really it is a heuristic means to stimulate discussion, rather than an attempt to calculate a quantifiable result. As such, it is not without its faults  – as both Drake and Sagan frequently noted. So much so, that the equation itself has been the subject of contention rather than spurring discussion on SETI. So should it now be revised?

The problem is that several of the parameters are actually either limited, potentially meaningless or now outdated. R*, for example, is limited as a) it disallows for the potential of extra-galactic civilisations, and b) it only considers stars of a similar spectral type to our own, which we now know are in the minority, whilst the vast majority of exoplanets so far discovered orbit stars of other spectral types. Meanwhile, fi leans towards planets similar to Earth only being capable of supporting life – but our evolving understanding of the solar system and the multiple places within it:  Titan, Mars, Enceladus, Europa, even the upper atmospheres of Jupiter, Venus and Saturn – shows us that life can start in many environments;  so it is possible that intelligent life could arise in planetary environments very different to our own.

Then there’s the fact that the equation is predicated on the idea of radio communication (fc, and L). These are both outmoded ways of thinking, and have inherent faults.

fc, for example, assumes we’ll be listening across all likely frequencies in all directions all the time, and that an alien civilisations will likewise be broadcasting in all directions all the time. But the reality is that our ability is limited: we must cycle our away around the sky, listening for a period of time before moving on. It is possible that an alien civilisation might be similarly limited, beaming signals in specific directions around their sky for specific periods of time before moving on to the next target. Thus, if we’re to hear them, we need to be listening at the exact right point in our sky at the exact time their signal arrives.

L similarly assumes the communication will come via a transmissible source. But what about those who opt to try to communicate via space probes, either in the manner we’d tried with the Voyager and Pioneer missions, or with more advanced craft specifically targeting the star systems around their own? given the vastness of interstellar distances, such probes might actually outlive their originating civilisations, rendering L moot. And what about our increasing potential to detect signs of life remotely through other means, such as by observing exoplanets and their atmospheres through increasingly capable telescopes that allow us to indirectly surmise the presence of life and possibly intelligence?

Given all these issues, John Gertz – a film producer, amateur astronomer and the three-term former chairman of the board for the SETI Institute has proposed a revised equation, thus:

N = ns x fp x ntb x fl x fi x fd x L

Where:

  • ns is the number of spots on the sky within our FOVs
  • fp is the fraction of stars with planets
  • ntb is the average number of bodies within each that could engender life
  • fl is the fraction of those that actually do give birth to life.
  • fi is the fraction of systems with life that evolves technological intelligence
  • fd is the fraction of technological life that is detectable by any means
  • L is the duration of detectability.

These parameters update up the equation by taking into account anything we can see in out current field of view, either within our galaxy or beyond it, whilst also taking into account that the majority of exoplanets – 4,383 and counting – are not actually similar to our Sun (fp), the potential for planets outside of what is regarded as a star’s “habitable zone” to develop life (ntb), as well as considering that we might detect other intelligences via artefacts other that direct communication (fd).

The Gertz Equation has been put forward for peer review and discussion within several science journals, and if accepted, could make the Drake Equation more relevant to modern discussions around SETI, rather than being a point of contention.