As the global population explosively grows over the past decades, the exhaustion of energy has become a hot topic among scientists. Thus, scientists started to care about the potential colonial life on another planet, the Mars. Whether there exists a biological or microbial life on Mars become crucial for understanding the Martian living conditions. To study this, one can study the existence of methane in the Martian atmosphere. Methane is a by-product by organisms, thus, if scientists find consistent existence of methane on Martian atmosphere, this will suggest the existence of active biological activity. The Trace Gas Orbiter (TGO) mission on 2016, which belongs to the Mars exploration program lead by NASA, carried instruments that allows it to perform detailed measurements on the Martian atmosphere and trace the location of specific gases. The newest result of TGO provided key analysis of the methane concentration, and it suggests that the concentration of methane has an upper limit of 0.05, which indicates a low methane distribution over the Martian surface. It will finish collecting data in 2020, by then, scientists can analyse and consider the possible atmospheric destruction process that will be a potential influencer on the methane concentration.
Mars as a close neighbor of Earth in the solar system was considered one of the planets that existed life on it. In the solar system, the 8 planets are attracted by the Sun and orbit around it. However, there are potential pieces of evidence that shown the orbit of each planet is continuously changing due to the change in the magnetic field of the Sun. Thus, billions of years ago, the distance between Mars and the Sun was closer than now, which will provide Mars with enough heat and gravity to generate hydrosphere which provides potential conditions for the rise of life. Scientists believe that there is a period in the early Martian atmosphere, there contains a lot of hydrogen that comes from the volcanic activity of Mars . All of these leads to the potential implication of life on early Mars.
As the position of Mars changed, right now the environment of Mars seems to be harsh for any possible life. However, biological scientists who studied the extreme environment on Earth have found that there is life that could survive in the Mars-like simulated environment . They found that there is some type of microorganism that has developed the capability to allow them to survive in a cold and dry environment just like Martian surfaces. This result suggests a possibility of life’s existence on Mars even on present Mars.
Understanding life’s existence on Mars is crucial because it can give suggestions about exploring possible colonization on Mars in the future to help us understand the environment of Mars. Also, Mars has a relatively easier access compared to other planets in the solar system because of its low pressure on atmosphere and the close distance to earth, understanding the life existence on Mars will provide human more understanding of our solar systems and if scientists could find possible microbial existence on Mars, it will become a valuable sample for us to study to make a progress on our medication and biology.
The earliest evidence that suggests the possible life activity is brought by the Viking experiment package in 1976, it demonstrates the possible existence of metabolism on Mars. Both of its landers received positive responses which suggested microbial life . Drastic debates had arisen about whether this product is produced by chemical reaction or life. The reason for the Viking experiment’s conclusion which suggests life on Mars is that methane is the by-product of biological activity and is a common element in the earth’s atmosphere. Moreover, methane tends to decompose when exposing to ultraviolet from the sun, thus, the recent detect of methane will be an important indicator of biological life existence on Mars within the several hundred years. Therefore, if scientists can find the evidence shows that there is methane exists in the Martian surface, it will become strong evidence of recent microbial life on Mars. Until now, scientists believe that the potential methane origin on Mars will be from the subsurface process and exogenous process , which will increase the difficulties of identifying the reasons for methane. Scientists need to distinguish between these two types of origin: exogenous process and subsurface process. For exogenous processes, the existence of methane is brought by the interstellar dust and meteorites, whereas the subsurface process is the one that scientists are looking for.
The ExoMars program that leads by NASA has been aiming in conducting research on Mars since the 1990s. One of its mission, the 2016 ExoMars Trace Gas Orbiter (TGO), was launched to Mars on March 14, 2016, and arrived on Mars on October 19, 2016. It aimed at collecting elements in the Martian atmosphere to study the trace of difference gas. It carried instruments that enable it to analyze the atmospheric condition on Mars and monitors the influence of seasonal change to the Martian atmosphere. Its key role during its 5-year mission time on Mars is to conduct data analyzation on the Martian atmosphere and spot possible composition of methane on the Martian atmosphere, at the same time acquire information about the trace gas including oxides and water vapors. It will also trace out the origin of these gases and send back the most detailed image about Martian surfaces. TGO will also help land the rover, Schiaparelli (EDM) to Mars and act as data and communication support. The main goal of EDM is to test the controlled landing technology and conduct research on Martian soils and send back the analyzations1
Description of Mission
The ExoMars program was started in 2001 and lead by the EAS. Its main goal was to explore Mars and find the possible signatures of life on Mars as Mars has an earth-like environment in the past. NASA joined the program in 2009 to help with technical and financial support. As Mars is treated as the main target for exobiology, scientists would like to obtain a sample for detailed study , thus, scientists want to study this by analyzing the gas contained in the Martian atmosphere. The fitful detection of methane since 2003 has brought significant scientific attention, thus, the 2016 ExoMars is the first launch in this program that send an orbiter and a lander that carried instruments to Mars, its result will allow scientists to have further study on this current topic.
The 2016 ExoMars mission’s key task is to bring back the sample of Martian surface and atmosphere for farther study on biosignature on Mars. This mission includes the Trace Gas Orbiter (TGO) and the Demonstrator Module (EDM), a rover called Schiaparelli that will land on the Martian surface and collect a surface sample for future analyses. The during the time of the mission, the TGO and EDM will conduct several important scientific investigations includes the search for any past or present biosignature of life, investigate the Martian atmosphere trace gas with their source and explore the Martian surfaces to provide a more detailed geological map8. The objective of TGO is to collect data from the Martian atmosphere to study the existence of CH4 and any other constituents in the atmosphere, it will also help the landing of EDM so that the rover can start to seek any evidence of biological process on the surface of Mars .
The TGO and Schiaparelli were sent to the Mars on March 16, 2016, on a proton rocket. Making use of the trajectory of Mars and Earth, its cruise time in space decrease to 7 months, and the orbiter and the lander have successfully arrived on Mars on Oct 2016. The TGO has been inserted into the orbit of Mars in Oct 2016 and after several practices of orbiting change, it will adjust to the best angle so that it can cover the optimum surface of Mars to help it collect data . It will also be eventually entering the 400km altitude of the Martian atmosphere and started data collecting.
Although the detection of methane will provide strong evidence of a biological process, scientists also need to pay attention to distinguishing the methane as a result of the geological process or the biological process. TGO brings payload that allows it to analyze between these two. The orbiter will fly over the Martian surface at the 400 km altitude to collect sample gas, and to increase accuracy, it will collect data from 3 different locations during its orbit around Mars to determine the possible source of gas .
As the TGO will work high in the sky of Mars, most of the data collection on the Martian surface will depend on the Entry, descent, landing Demonstrator Module, Schiaparelli. Its main role is to test the present technology for safely landing and the experience will be used in future human mission to the Mars8, also, once it successfully lands on Mars, one of the sensors that on Schiaparelli, meteorological station, will start to generate weather condition around its landing site including the soil, humidity, and temperature, it will study the electric properties on Mars. Its data will bring valuable information about the environment property of the Martian surface for scientists to have deepening understanding about the surface of Mars and identify the possible places that will have life signatures.
What’s noticeable is that the mission time for Schiaparelli since October is autumn for the northern part of Mars and it is the season for the dust storm. Scientists have to take the rich dust in the air into account when planning the landing and descent of Schiaparelli. They need to consider the increase of friction due to the dust and the material used for the parachute. At the same time, the data conduction will take place in a dusty area, which will provide information for scientists to study the properties of Mars during the dusty season.
The duration of this mission will last for about 6 years and end in 2022, including the standard mission on Mars and an innovative part. After the release of Schiaparelli, the TGO will start to adjust its orbit to ultimate data collection using aerobraking. This is the first time for EAS scientists to use aerobraking on the mission on Mars8. While aerobraking will slow the orbiter and lower its height, it will allow the orbiter to obtain an angle that will allow it to cover most of the Martian surface.
There are two elements of this mission —- the TGO and Schiaparelli to complete the precise data collection on Mars, scientists have prepared instruments that will help them to collect data in extreme environments on Mars and retain the preciseness of the data. To increase the sensitivity and detect the minor amount of gas, the spectrometers on TGO will allow it to detect a small amount of gas exist in the air of Mars and observe the different gas composition between different season. The Color and stereo surface imaging system on TGO will ensure the preciseness of the image of Martian surface that it sends back to Earth for scientists to study the possible structure of Mars, and the fine resolution epithermal neutron detector (FREND) will allow it to detect possible water hydrogen under or on the Martian surface which will help the scientist to find the possible location of water existence, which will lead to potential location for discovery of life8.
The entry, descent and landing demonstrator module Schiaparelli is about 1.65 m wide, and 1.8 m high, it carried DREAM (Dust characterization, Risk assessment and Environment Analyser on the Martian Surface) instrument that enables it to study the dust environment on Martian surface as the time it lands on Mars will be the Martian dust season; the panoramic camera on Schiaparelli will send back detailed pictures around the landing site and work together with infrared spectrometer on it to acquire information about the surface property that will increase its understanding about the dust season on Mars. The engineering measurement relay on the sensors and radars that locate on the outside part of the rover will provide valuable information during the descent, which will help scientists to make progression on the future mission8.
The landing site for Schiaparelli will be the Meridiani Planum, around the north part of Mars, on there, Schiaparelli will conduct research around its landing site for several days and send back the data to TGO. As the Meridiani Planum be a relatively smooth part of Mars, which will decrease the possibility of destroy during landing, it will give the heatshield enough time to slow down the falling speed of the rover and allow the thruster started to take control of the speed and result in a smooth landing .
As the time for Schiaparelli to land on Mars will be the active season for the dust storm, the engineering team make some special adjustments to ensure the successful landing of Schiaparelli. The equipment that will prepare the landing of Schiaparelli including the parachute system, a doppler radar for detect altitude, the heat shield to protect the rover when entering the atmosphere of Mars, a telemetry, tracking and command system and a liquid propulsion system to monitor its speed . As the weight of Schiaparelli to be 577 kg, it has to have enough propulsion to slow it down during the entering to protect the data platform inside the rover, as all these systems will work together to help it land successfully on Mars.
The Schiaparelli lander entered the Martian atmosphere on Oct 19, 2016, and intended to start collecting data on the same day, however, before it touched the ground, the scientists’ team lost its signal and it has been considered as crashed during the landing. This suggests the failure of the testing landing techniques and indicates future progresses that need to be made to help future Martian mission to land successfully. The exact reasons for the crash of Schiaparelli are stilling unknown and scientists are looking for it, it is known that the slow down process is smoothly processed . Although Schiaparelli did not successfully land on Mars, it collected nearly all of the data it needs before its crash, scientists will use those data to prepare the landing of future Martian rovers.
Although the lander did not land on Mars as planned, the Trace Gas Orbiter is operated well, and it has entered the orbit of Mars and started to take data in March 2018. The TGO is orbiting Mars every two hours now, and act as a data relay of the current land rovers on Mars. The first important result from TGO is the Martian dust storm. Since Mars has an extremely thin air, the dust particles in the air are rich and there is the seasonal dust storm happened in the northern part of Mars. According to the two spectrometers onboard, the NOMAD and ACS, there is noticeably increase of water vapors in the Martian surface during the dust storm in a high northern latitude . This observation reveals the information about the Martian climate and the circulation on this planet, which will lead to the study of the storage of solar energy on Mars. As the water ice clouds present on Mars, the water vapor ratio before the dust storm is below detectability below the altitude of 40km , this ratio increased suddenly when the dust storm begins, which suggests the increase in temperature during the dust storm so that there is no more water ice cloud. This face help scientists to understand the impact of dust storm to the climate change of Martian surfaces, at the same time, with the analysis of this result, under the influence of global dust storm on Mars, it is rare to find life exist on the surface of the Mars, and due to its influence on global circulation, any produce of methane will escape and disperse throughout a very short of period of time, which indicates the difficulties on detecting life existence.
The second important observation made by the TGO is related to its key interest—-the methane distribution and detection of Mars. Firstly, according to a recent detect of methane burst measured by the Curiosity rover on June 19, 2019, the amount of methane it detected is 21 ppbv (parts per billion by volume), the highest concentration scientists ever observed , however, the instruments on TGO did not sense any response of sudden methane burst, which lead to the understanding of the Martian global circulation model. There are two reasons that scientists considered that why TGO did not detect such bursts. The first one is that when TGO tries to measure the gas distribution that is close to the ground, the air becomes cloudy and dusty, which will infect the preciseness of the measurement. Also, due to the high-speed wind existed on the Martian surface, even though there is a high amount of methane that was there, when the time TGO measured that area, the methane probably has dispersed into the environment so that the concentration is too low for TGO to measure. Secondly, according to the summary and analysis of the measurement data sent back by the TGO during its operation, the result has suggested that the upper limit of the amount of methane in Martian atmosphere is as low as 0.05 ppbv, whereas the average amount of methane on Earth is 1800 ppbv .
These results lead scientists to the search of possible reasons for the quick dispersion of methane, as the analysis from the Curiosity rover detection of methane, the strong global wind circulation redistribution the methane before any scientific measurements can detect it, the complex Martian surface weather increase the difficulties of instruments to detect the possible hints of methane. Scientists need to, in the future, make progress of the measurement method in order to detect the possible hint of biosignature simultaneously.
According to the data collected by the Trace Gas Orbiter, the concentration of methane is very low on Mars, which indicates that there is a low possibility that there is life that existed on Mars right now. It also gives scientists important hints about the air circulation model on Mars as it analyzed the data it collected during the dust season on Mars, which suggests that during the dust storm, the water vapor in the air will suddenly increase. This illustrates the crucial influence brought by the dust storm to the Martian air circulation. We cannot draw any conclusion about the claim that there was life on Mars billions of years ago, although there are scientific papers that support this claim, since the failure of the lander, Schiaparelli, scientists of ESA cannot have soil sample from Mars to study this.
However, the test landing of Schiaparelli has provided valuable experiences for future Mars missions that will carry a robot or even astronaut. ESA has been preparing for the second part of the ExoMars program, which will send a lander to Mars in 2020. This 2016 mission has accumulated crucial experiences and act as a landing test. Scientists will make improvement on the parachute system on the rover, and according to the detailed image sent back by the TGO, they will be able to choose a more possible place that will have biosignature existed. This search of life program on Mars will significantly increase our understanding of exobiology.