Mitra is Vedic Deity,often mentioned along with Varuna,both called togehter as Mitra Varuna.
Mitra indicates dawn.
Varuna and Maitra are the sons of Aththi and Kasyapa.
So also Surya,the SunGod.
Worship of Surya is found throughout the world,with the attributes described in Hinduism.
Mitra Varuna is worshiped in the Middle east, Italy and throughout Europe.
And the Mayas,Incas,Mittanis,Akkadians,Sumerians and Egyptians were Sun worshippers.
The Popes Baptized with Warter, invoking Mitra Varuna.
These sons of Aththi and Kasyapa are Twelve.
They are called the Adhityas.
Lord Vishnu is on off the Adityas.
Lord Krishna states in the Bhagavad Gita ,
‘Adityanaam Aham Vishnu’
In Vibhuti Yoga.
In the daily oblations offered to Surya in Sandhyavandana,the morning Upasthana mantra offers oblations to Mitra thus.
Mitra also means friend.
One can find these names in the Adityahrudaya Stotra.
Srimad Bhagavatham states that all these are Forms of Surya,The Sun God.
‘In each month of the year, it is a different Aditya who shines as the Sun-God.As Indra, Surya destroys the enemies of the gods. As Dhata, he creates living beings. As Parjanya, he showers down rain. As Tvashta, he lives in the trees and herbs. As Pusha, he makes foodgrains grow. As Aryama, he is in the wind. As Bhaga, he is in the body of all living beings. As Vivasvana, he is in fire and helps to cook food. As Vishnu, he destroys the enemies of the gods. As Amshumana, he is again in the wind. As Varuna, he is in the waters and As Mitra, he is in the moon and in the oceans.’
Sun worship in Mesapotamia,Mittani Empire and Rome was from the Mitra Varuna of the Vedas.
These Deities are mentioned in the Zend Avestha of Parsis,Iran fron where this has traveled to Europe.
The Pagan Worship ,preceding Christianity had Mitra Varuna included.
‘The origin of the cult of Mithra dates from the time that the Hindus and Persians still formed one people, for the god Mithra occurs in the religion and the sacred books of both races, i.e. in the Vedas and in the Avesta. In Vedic hymns he is frequently mentioned and is nearly always coupled with Varuna, but beyond the bare occurrence of his name, little is known of him (Rigveda, III, 59). It is conjectured (Oldenberg, “Die “Religion des Veda,” Berlin, 1894) that Mithra was the rising sun, Varuna the setting sun; or, Mithra, the sky at daytime, Varuna, the sky at night; or, the one the sun, the other the moon. In any case Mithra is a light or solar deity of some sort; but in vedic times the vague and general mention of him seems to indicate that his name was little more than a memory. In the Avesta he is much more of a living and ruling deity than in Indian piety; nevertheless, he is not only secondary to Ahura Mazda, but he does not belong to the seven Amshaspands or personified virtues which immediately surround Ahura; he is but a Yazad, a popular demigod or genius. The Avesta however gives us his position only after the Zoroastrian reformation; the inscriptions of the Achaemenidae (seventh to fourth century B.C.) assign him a much higher place, naming him immediately after Ahura Mazda and associating him with the goddess Anaitis (Anahata), whose name sometimes precedes his own. Mithra is the god of light, Anaitis the goddess of water. Independently of the Zoroastrian reform, Mithra retained his place as foremost deity in the northwest of the Iranian highlands. After the conquest of Babylon this Persian cult came into contact with Chaldean astrology and with the national worship of Marduk. For a time the two priesthoods of Mithra and Marduk (magi and chaldaei respectively) coexisted in the capital and Mithraism borrowed much from this intercourse. This modified Mithraism traveled farther northwestward and became the State cult of Armenia. Its rulers, anxious to claim descent from the glorious kings of the past, adopted Mithradates as their royal name (so five kings of Georgia, and Eupator of the Bosporus). Mithraism then entered Asia Minor, especially Pontus and Cappadocia. Here it came into contact with the Phrygian cult of Attis and Cybele from which it adopted a number of ideas and practices, though apparently not the gross obscenities of the Phrygian worship. This Phrygian-Chaldean-Indo-Iranian religion, in which the Iranian element remained predominant, came, after Alexander’s conquest, in touch with the Western World. Hellenism, however, and especially Greece itself, remained remarkably free from its influence. When finally the Romans took possession of the Kingdom of Pergamum, occupied Asia Minor and stationed two legions of soldiers on the Euphrates, the success of Mithraism in the West was secured. It spread rapidly from the Bosporus to the Atlantic, from Illyria to Britain. Its foremost apostles were the legionaries; hence it spread first to the frontier stations of the Roman army.
Mithraism was emphatically a soldier religion: Mithra, its hero, was especially a divinity of fidelity, manliness, and bravery; the stress it laid on good fellowship and brotherliness, its exclusion of women, and the secret bond amongst its members have suggested the idea that Mithraism was Masonry amongst the Roman soldiery. At the same time Eastern slaves and foreign tradesmen maintained its propaganda in the cities. When magi, coming from King Tiridates of Armenia, had worshipped in Nero an emanation of Mithra, the emperor wished to be initiated in their mysteries. As Mithraism passed as a Phrygian cult it began to share in the official recognition which Phrygian worship had long enjoyed in Rome. The Emperor Commodus was publicly initiated. Its greatest devotee however was the imperial son of a priestess of the sun-god at Sirmium in Pannonia, Valerian, who according to the testimony of Flavius Vopiscus, never forgot the cave where his mother initiated him. In Rome, he established a college of sun priests and his coins bear the legend “Sol, Dominus Imperii Romani”. Diocletian, Galerius, and Licinius built at Carnuntum on the Danube a temple to Mithra with the dedication: “Fautori Imperii Sui”. But with the triumph of Christianity Mithraism came to a sudden end. Under Julian it had with other pagan cults a short revival. The pagans of Alexandria lynched George the Arian, bishop of the city, for attempting to build a church over a Mithras cave near the town. The laws of Theodosius I signed its death warrant. The magi walled up their sacred caves; and Mithra has no martyrs to rival the martyrs who died for Christ.’
The above Link is Catholic Encyclopedia.
Now excerpts from Russain Veda,Perun,from research Scholars on how the Roman Emperors and Popes worshiped Mitra -Varuna
And how Pope Hadrian Baptised with Varuna,the God of Water / Ocean.
I Robertson and others tell us that both Christianity existed almost exactly the same cult of the god Mithras, whose name, I think, comes from the Hebrew Inscription MTP, which means irrigation, 1 t. e. baptized in water (according to the Roman rite). Hence it is likely to occur, and the name of the spiritual crown-miter (mitra Italian and Greek?????),and the word of the Metropolitan as a difference in the Greek and Latin spelling proves nothing: in other nomadic names it Many significant.
During the time of Hadrian, t. E., According to our comparisons of Honorius (395-423), if the case is not about the pope Hadrian, structures that “baptism in water” were,-says archaeologist Wright 2-scattered across Britain, South of France, Spain Germany, Dalmatia, Dacia and North Africa. In all the cities and forts, located in Italy and along the banks of the Rhine and Danube were Mithraeum (t. E. Baptistery with water). «Mitraism, says John Robertson in his book« Pagan Christs»,t. E ..” Pagan Christs», -was in point of range the most nearly universal religion of the Western World in the early centuries of the Christian era 3(Mithraism was almost universal religion of Western Europe in the first centuries of the Christian era). In England, it was found by an artificial grotto with sculptures of services Mitra and the inscription “God, the best and greatest, the invincible Mithra, the god of the ages”, and in Kichestere been with the same inscription: “God the Sun, the invincible Mithra, the god of the ages.” Others are the same found in Cumberland, near Oxford, near London, near York, near Manchester, and so on.. In Rome and its surroundings were a number of these same caves; they existed in Egypt and probably in West Asia. Only in Greece, they were few at this imenem ‘( https://www.politforums.net/eng/other/1336328618.html )