Each and every navagraha has one diety associated with that planet, these gods literally represents all the qualities of that planet.Human being over different life cycles acquire blessings or lessons from these god s on the basis of their individual karmas.

These karmas which are recorded by natural forces and their gods[Eg: Lord Vayu is everywhere] are then judged by dieties and our good karmas and bad karmas both manifest as our current life journeys. Good karmas which is carried over in our current life manifest as blessings by the gods which result in our birth in dharmic families, our career progression,health and wealth we will acquire.

Bad karmas and deeds done in previous life are punished by the gods and they manifest in our current lives as long as we don't learn the lessons associated with that punishment. These punishment depends on the severity of the bad karma acquired and manifest as health issues,loss of wealth, family problems, struggle in career and also bad luck.

Each and every seeker in sanatana dharma possess the right to reduce this malefic effect by perfomring good deeds, going on tirth yatras to honor the gods and chanting mantras.

But how do you identify if you have any doshas pertaining to a planet? For this, you need to understand few concepts of astrology and also observe the current state of your life.
Upon your birth, the exact time and date are asked by a Jyotisha to prepare a birth chart. In any birth chart, 4 sections are made by diagonally intersecting a rectangular box. In one section, we have 3 more subsection and in total we have 12 setions of a box.

These 12 section represent the 12 zodiac or rashis of any individual. And in these 12 rashis we have 9 planets which sit according to your time and date of birth. Any good jyotisha pandit or priest looks and studies this birth chart to identify your strong and weak planets.On the basis of planetary positioning, he advices you few things which aid in your personal life planning. These tips from the priest usually involves how your health will look, what kind of life partners you will find, the amount of wealth you will acquire, the hardships you will follow and also your spiritual devotion towards the gods.

These 9 planets according to Vedic Hierarchy from greatest influence to lowest are Sun[रवि], Moon[चन्द्र], Mars[मंगल], Mercury[बुधः], Jupiter[गुरु], Venus[शुक्र], Saturn[शनि], Rahu[राहु], Ketu[केतु]. Placement of these planets in favourable position means you performed good deeds in previous life and unfavourable posiotion means, you need to strengthen that particular planet(s).

If you have doshas for any individual planet, they can be reduced by chanting indivdual mantras associated with that particular planet.

Let us now understand the 9 planets according to their hierarchy, their associated dieties, and mantras to reduce their maleific effects.

Surya

Surya or Sun god is the primary diety of all navagraha and responsible for wisdom and immense spiritual light. According to Jyotisha, the sun signifies leadership skills, honor in society, authority, and favor from the government and is responsible for giving shape, personality, and future to life or an event. Sun also represents the father's side of the family. Any dosha which reduce the blessings of the sun god can be reduce by Conscious chanting of these mantras.

Surya Beej Mantra

ॐ ह्रां ह्रीं ह्रौं सः सूर्याय नमः ॥
Om Hraam Hreem Hraum Sah Suryay Namah||

Surya Gayatri Mantra

ॐ सप्त-तुरंगाय विद्महे सहस्र-किरणाय धीमहि तन्नो रविः प्रचोदयात्||
Om Sapt Turangay Vidhmahe Sahasra Kirnay Dheemahi Tanno Ravi Prachodyat||

Aditya Gayatri Mantra

ॐ आदित्याय विद्महे मार्त्तण्डाय धीमहि तन्नः सूर्यः प्रचोदयात् ॥
Om Aadityay Vidhmahe Martanday Dheemahi Tanah: Surya: Prachodyat||

Chandra

Chandra or moon god is also called Soma,Indu,atrisuta and many other names. Moon is responsible for the feminine aspect for human life and also our Mother's side of the family.

Chandra Beej Mantra.

ॐ श्रां श्रीं श्रौं सः चंद्राय नमः ॥
Om Shraam Shreem Shraum Sah: Chandray Namah ॥

Chandra Gayatri Mantra

ॐ क्षीर-पुत्राय विद्महे अमृत-तत्त्वाय धीमहि तन्नो सोमः प्रचोदयात् ॥
Om Ksheer Putray Vidhmahe Amrit Tatvay Dheemahi Tanno Somah: Prachodyat ॥

Mangala

Mangala or mars god is considered as son of Bhoomi Mata or Mother earth. When earth was lying in the ocean out of its orbit, the varaha avatar of Shri Vishu lifted it on its tusk and placed it in our current orbit. Mars is a masculine planet by nature which rules courage and confidence.

Mangal Beej mantra

ॐ क्रां क्रीं क्रौं सः भौमाय नमः॥
Om Kram Kreem Kraum Sah: Bhaumay Namh||

Mangal Gayatri mantra

ॐ अंगारकाय विदमहे शक्ति-हस्ताय धीमहि तन्नो भौमः प्रचोदयात्॥
Om Angarkay Vidhmahe Shakti Hastay Dheemahi Tanno Bhauma: Prachodyat॥

Buddha

Buddha or mercury god was born out of the union of Moon and Tara. Buddha represents our communication abilities anf respiratory related diseases.

Buddha Beej mantra

ॐ ब्रां ब्रीं ब्रौं सः बुधाय नमः ॥
Om Braam Breem Braum Sah: Budhay Namah॥

Buddha Gayatri mantra

ॐ सौम्य-रूपाय विदमहे वाणेशाय धीमहि तन्नो सौम्यः प्रचोदयात् ॥
Om Saumya Rupay Vidhmahe Vaaneshay Dheemahi Tannoh: Saumya Prachodyat॥

Brihaspati

Brihaspati or Jupiter god is considered as an auspicious planet in hindu myhrology. Brihaspati is the teacher of all devas and bestpws the seeker with knowledge, light, health and wealth to improve our karmas. Ill placement of jupiter in our chart give the seeker blood related problems and also diabetes.

Brishapati Beej mantra

ॐ ग्रां ग्रीं ग्रौं सः गुरूवे नमः ॥
Om Graam Greem Graum Sah: Gurve Namah॥

Brishapati Gayatri mantra

ॐ अंगि-रसाय विदमहे दण्डायुधाय धीमहि तन्नो जीवः प्रचोदयात् ॥
ॐ वृषभध्वजाय विद्महे करुनीहस्ताय धीमहि तन्नो गुरु: प्रचोदयात् ॥
ॐ गुरुदेवाय विद्महे परब्रह्माय धीमहि तन्नो गुरु: प्रचोदयात् ॥

Om Angirsaay Vidhmhe Dandaayudhay Dheemahi Tanno Jeev: Prachodayat ॥
Om Vrishabadhwajaaya Vidmahae Kruni Hastaaya Dheemahi Tanno Guru: Prachodayat ॥
Om Gurudevaay Vidhmhe Parbrahmaay Dheemahi Tanno Guru Prachodyat ॥

Shukra

Shukra or Venus god symbolizes love, passion, marriage and beauty. Shukra is usually considered in the context of determinig the type of life long partner one gets. Shukra is the son of Sage Bhrigu and also the perceptor of Asuras where they refer to him as shukracharya.

Shukra Beej mantra

ॐ द्रां द्रीं द्रौं सः शुक्राय नमः ॥
Om Draam Dreem Draum Sah Shukray Namah॥

Shukra Gayatri mantra

ऊँ भृगुवंशजाताय विद्यमहे श्वेतवाहनाय धीमहि तन्न: शुक्रः प्रचोदयात्॥
ॐ भृगुपुत्राय विद्महे श्वेतवाहनाय धीमहि तन्नः कवि: प्रचोदयात्॥

Om Bhrighu Vansh Jaatay Vidhmahae Shwet Vahnay Dheemahi Tannho Shukrah Prachodyat॥
Om Bhrighputray Vidhmahe Shwet Vahnay Dheemahi Tannho Kavih Prachodyat॥

Shani

Shani or lord saturn is the son of Surya Deva and Chayya Devi. Saturn is a slow moving planet and is considered inauspicious in hindu adtrology. Saturn is known for it hard judgement and law of karma, he blesses the devotees on the basis of his karma in past lifes.

Mantra to honor and invoke shani devata.

ॐ ऐं ह्रीं श्रीं शनैश्चराय नमः ||
Om Aing Hring Shring Shanaishchray Namah ||

Shani Beeja mantra

ॐ प्रां प्रीं प्रौं सः शनैश्चराय नमः॥
Om Praam Preem Praum Sah: Shanishchray Namah॥

Shani Gayatri mantra

ॐ भग-भवाय विदमहे मृत्यु-रूपाय धीमहि तन्नो शनिः प्रचोदयात् ॥
ॐ काकध्वजाय विद्महे खड्गहस्ताय धीमहि तन्नो मन्दः प्रचोदयात् ॥

Om Bhagabhavaya Vidmahaim Mrityu-rupaya Dheemahi tanno Shanih Prachodyat॥
Om Kaakadhwajaaya Vidmahae Khadga Hastaaya Dheemahi Tanno Mandah Prachodayat॥

Rahu

Rahu represents the obsessions and desires in human beings. Unlike the other eight, Rahu is a shadow entity that causes eclipses and is the king of meteors.

Rahu beeja mantra

ॐ भ्रां भ्रीं भ्रौं सः राहवे नमः॥
Om Bhraam Bhreem Bhraum Sah: Rahve Namah॥

Rahu Gayatri mantra

ॐ शिरो-रूपाय विदमहे अमृतेशाय धीमहि तन्नो राहुः प्रचोदयात्॥
ॐ नाकाध्वजाय विद्महे पद्माहस्ताय धीमहि तन्नो राहू: प्रचोदयात्॥
ॐ नीलवर्णाय विद्महे सैंहिकेयाय धीमहि तन्नो राहुः प्रचोदयात्॥

Om Shiro Rupaay Vidhmhe Amrateshaay Dheemahi Tanno Rahu: Prachodyat॥
Om Naakadhwajaaya Vidmahae Padma Hastaaya Dheemahi Tanno Raahu: Prachodayaat॥
Om Neelvarnaay Vidhmahe Sainhikaay Dheemahi Tanno Rahu Prachodyat॥

Ketu

Ketu is considered to be a half planet, the south, or descending node of the Moon. Ketu helps people incline towards a spiritual wau of living and is considered to be the reason for liberation or Moksha.

Ketu beeja mantra

ॐ स्रां स्रीं स्रौं सः केतवे नमः॥
Om Sraam Sreem Sraum Sah Ketave Namah॥

Ketu Gayatri mantra

ॐ पद्म-पुत्राय विदमहे अमृतेशाय धीमहि तन्नो केतुः प्रचोदयात्॥
ॐ गद्दाह्स्ताय विद्महे अमृतेशाय धीमहि तन्न: केतु: प्रचोदयात्॥
ॐ अश्वाध्वजाय विद्महे शूलाहस्ताय धीमहि तन्नो केतु: प्रचोदयात्॥

Om Padam Putray Vidhmahe Amriteshaay Dheemahi Tanno Ketu Prachodyat॥
Om Gaddahstaay Vidhmahe Amrateshaay Dheemahi Tannho Ketu Prachodyat॥
Om Aswadhwajaaya Vidmahae Shoola Hastaaya Dheemahi Tanno Ketu Prachodayat॥

This summarizes all the mantra associated with navagraha. Conscious chanting of this mantras on days associated with 7 planets can reduce the doshas associated with that planet.